Newsletter No. 16 III-N Technology

Transcription

GANEX
Newsletter No. 16
April 2014
III-N Technology
Coordinated by CRHEA-CNRS research laboratory, this monthly newsletter is produced
by Knowmade with collaboration from the managers of GANEX groups. The newsletter
presents a selection of newest scientific publications, patent applications and press
releases related to III-Nitride semiconductor materials (Ga, AlN, InN and alloys)
All issues on www.ganex.fr in Veille section.
Free subscription http://www.knowmade.com/ganex.html
GANEX
Cluster of Excellence (Labex, 2012-2019)
GANEX is a cluster gathering French research teams involved in GaN technology. The objective of GANEX
is to strengthen the position of French academic players in terms of knowledge and visibility, and
strengthen the French industrials in terms of know-how and market share.
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METHODOLOGY
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GANEX | Newsletter No. 16 - III-N Technology
2
TABLE OF CONTENTS
(clickable links to chapters)
SCIENTIFIC PUBLICATION ................................................................................................................... 4
GROUP 1 - LEDs and Lighting ................................................................................................................... 4
GROUP 2 - Laser and Coherent sources ................................................................................................... 8
GROUP 3 - Power Electronics ................................................................................................................... 9
GROUP 4 - Advanced Electronics and RF ............................................................................................... 14
GROUP 5 - Sensors and MEMS............................................................................................................... 19
GROUP 6 - Photovoltaics and Energy harvesting ................................................................................... 23
GROUP 7 - Materials, Technology and Fundamental............................................................................. 25
PRESS RELEASE ................................................................................................................................ 34
PATENT APPLICATION...................................................................................................................... 51
KnowMade
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SCIENTIFIC PUBLICATION
Selection of new scientific articles
GROUP 1 - LEDs and Lighting
Group leader: Benjamin Damilano (CRHEA-CNRS)
Information selected by Benjamin Damilano (CRHEA-CNRS)
Fabrication and optical characteristics of
phosphor-free InGaN nanopyramid white light
emitting
diodes
by
nanospherical-lens
photolithography
Kui Wu1,2, Tongbo Wei1,a), Haiyang Zheng1, Ding
Lan3, Xuecheng Wei1, Qiang Hu1, Hongxi Lu1, Junxi
Wang1, Yi Luo2 and Jinmin Li1
1 State Key Laboratory of Solid-State Lighting, Institute
of Semiconductors, Chinese Academy of Sciences,
Beijing 100083, China
2 Department of Electronic Engineering, Tsinghua
National Laboratory for Information Science and
Technology/State Key Lab on Integrated
Optoelectronics, Tsinghua University, Beijing
100084,China
3 National Microgravity Laboratory, Institute of
Mechanics, Chinese Academy of Sciences, Beijing
100080, China
LEDs may have great potential for highly efficient
white lighting.
Experimental verification of effects of barrier
dopings on the internal electric fields and the
band structure in InGaN/GaN light emitting
diodes
Jung-Hoon Song1, Tae-Soo Kim1, Ki-Nam Park1, Jin-Gyu
Lee1, Soon-Ku Hong2,a), Sung-Royng Cho3, Seogwoo
Lee3 and Meoung Whan Cho3
1 Department of Physics, Kongju National University,
Kongju, Chungnam 314-701, South Korea
2 Department of Advanced Materials Engineering,
Chungnam National University, Daejeon 305-764,
South Korea
3 Wasvesquare Co., Inc., Yongin, Gyeonggi 449-863,
South Korea
Applied Physics Letters
Vol. 104, 121114 (2014);
http://dx.doi.org/10.1063/1.4870256
Journal of Applied Physics
Vol. 115, 123101 (2014);
http://dx.doi.org/10.1063/1.4869336
A novel nanopattern technique of nanosphericallens photolithography is introduced to fabricate
the InGaN nanopyramid white (NPW) lightemitting diodes (LEDs) by selective area growth.
Highly ordered NPW LED arrays are achieved after
optimizing the growth conditions. It is found that
the NPW LEDs vary from warm white light to cool
with the increase in growth temperature. For the
cool white NPW LEDs, the spectrum is similar to
the conventional white LEDs obtained from the
blue LEDs combined with yellow phosphors. The
blue emission originates from the upper sidewalls
of nanopyramids, and yellow light is mainly
emitted from the lower ridges with respect to the
base of nanopyramids. Furthermore, simulation
shows that the light extraction efficiency of NPW
LEDs is about 4 times higher compared with
conventional ones, and the escape cone is as
much as 85° due to their three-dimensional
nanopyramid structures. These observations
suggest that the proposed phosphor-free NPW
We experimentally clarify the effects of barrier
dopings on the polarization induced electric fields
and the band structure in InGaN/GaN blue light
emitting diodes. Both effects were independently
verified by using electric field modulated
reflectance
and
capacitance-voltage
measurement. It is shown that the Si barrier
doping does reduce the polarization induced
electric field in the quantum wells. But the benefit
of Si-doping is nullified by modification of the
band structure and depletion process. With
increased number of doped barriers, smaller
number of quantum wells remains in the
depletion region at the onset of the diffusion
process, which can reduce the effective active
volume and enhance the electron overflow.
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On the mechanisms of InGaN electron cooler in
InGaN/GaN light-emitting diodes
Zi-Hui Zhang,1 Wei Liu,1 Swee Tiam Tan,1 Zhengang
Ju,1 Yun Ji,1 Zabu Kyaw,1 Xueliang Zhang,1 Namig
Hasanov,1 Binbin Zhu,1 Shunpeng Lu,1 Yiping Zhang,1
Xiao Wei Sun,1,3 and Hilmi Volkan Demir1,2,*
1LUMINOUS! Centre of Excellence for Semiconductor
Lighting and Displays, School of Electrical and
Electronic Engineering, Nanyang Technological
University, 50 Nanyang Avenue, 639798, Singapore
2Department of Electrical and Electronics, Department
of Physics, and UNAM-Institute of Material Science and
Nanotechnology, Bilkent University, TR-06800, Ankara,
Turkey
Optics Express
Vol. 22,Issue S3, pp. A779-A789 (2014)
http://dx.doi.org/10.1364/OE.22.00A779
Electron overflow limits the quantum efficiency of
InGaN/GaN light-emitting diodes. InGaN electron
cooler (EC) can be inserted before growing
InGaN/GaN multiple quantum wells (MQWs) to
reduce electron overflow. However, detailed
mechanisms of how the InGaN EC contributes to
the efficiency improvement have remained
unclear so far. In this work, we theoretically
propose and experimentally demonstrate an
electron mean-free-path model, which reveals the
InGaN EC reduces the electron mean free path in
MQWs, increases the electron capture rate and
also reduces the valence band barrier heights of
the MQWs, in turn promoting the hole transport
into MQWs.
A quantitative method for determination of
carrier escape efficiency in GaN-based lightemitting diodes: A comparison of open- and
short-circuit photoluminescence
Seung-Hyuk Lim1, Young-Ho Ko1 and Yong-Hoon
Cho1,a)
1 Department of Physics and KI for the Nanocentury,
Korea Advanced Institute of Science and Technology
(KAIST), Daejeon 305-701, South Korea
Vol. 104, 091104 (2014);
http://dx.doi.org/10.1063/1.4867238
We propose a method to quantitatively analyze
the internal quantum efficiency (IQE) as well as
the efficiencies of non-radiative recombination in
the active region (NRA) and carrier escape out of
the active region (ESC) by comparing open-circuit
(OC) to short-circuit (SC) conditions of InGaNbased light-emitting diodes (LEDs). First, the IQE
was extracted from excitation-power dependent
photoluminescence at low temperature, and the
electron-hole wavefunction overlaps were
calculated under OC and SC conditions. Then, the
NRA and ESC efficiencies were quantitatively
deduced and also compared with photocurrent
data. The proposed method would be useful for
assessing and designing quantum barriers and
analyzing leakage current in LEDs.
High-Efficiency and Crack-Free InGaN-Based LEDs
on a 6-inch Si (111) Substrate With a Composite
Buffer Layer Structure and Quaternary
Superlattices Electron-Blocking Layers
Li, Z. , Lee, C. ; Lin, D. ; Lin, B. ; Shen, K. ; Chiu, C. ; Tu, P.
; Kuo, H. ; Uen, W. ; Horng, R. ; Chi, G. ; Chang, C.
Department of Photonics and Institute of ElectroOptical Engineering, Hsinchu, Taiwan
Quantum Electronics, IEEE Journal of
Volume:50 , Issue: 5 , May 2014
Page(s): 354 - 363
http://dx.doi.org/10.1109/JQE.2014.2304460
In this paper, a composite buffer layer structure
(CBLS) with multiple AlGaN layers and grading of
Al
composition/u-GaN1/(AlN/GaN)
superlattices/u-GaN2
and
InAlGaN/AlGaN
quaternary superlattices electron-blocking layers
(QSLs-EBLs) are introduced into the epitaxial
growth of InGaN-based light-emitting diodes
(LEDs) on 6-inch Si (111) substrates to suppress
cracking and improve the crystalline quality and
emission efficiency. The effect of CBLS and QSLsEBL on the crystalline quality and emission
efficiency of InGaN-based LEDs on Si substrates
was studied in detail. Optical microscopic images
revealed the absence of cracks and Ga melt-back
etching. The atomic force microscopy images
exhibited that the root-mean-square value of the
surface morphology was only 0.82 nm. The full
widths at half maxima of the (0002) and
$(10overline{1}2)$ reflections in the double
crystal X-ray rocking curve were ${sim}{330}$ and
450 arcs, respectively. The total threading
dislocation density, revealed by transmission
electron microscopy, was ${<}{rm 6}times
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10^{8}~{rm cm}^{-2}$ . From the material
characterizations, described above, blue and
white LEDs emitters were fabricated using the
epiwafers of InGaN-based LEDs on 6-inch Si
substrates. The blue LEDs emitter that comprised
blue LEDs chip and clear lenses had an emission
power of 490 mW at 350 mA, a wall-plug
efficiency of 45% at 350 mA, and an efficiency
droop of 80%. The white LEDs emitter that
comprised blue LEDs chip and yellow phosphor
had an emission efficiency of ${sim}{rm 110}~{rm
lm}/{rm W}$ at 350 mA and an efficiency droop of
78%. These results imply that the use of a CBLS
and QSLs-EBL was found to be very simple and
effective in fa- ricating high-efficiency InGaNbased LEDs on Si for solid-state lighting
applications.
1 Institut d’Electronique Fondamentale, UMR 8622
CNRS, Université Paris Sud XI, 91405
Orsay cedex, France
2 St. Petersburg Academic University, Nanotechnology
Research and Education Centre,
Russian Academy of Science, Khlopina 8/3, 194021 St.
Petersburg, Russia
3 Ioffe Physical-Technical Institute of the Russian
Academy of Science, Polytechnicheskaya
26, 194021 St. Petersburg, Russia
4 ICMP LOEQ Ecole Polytechnique Fédérale de
Lausanne, 1015 Lausanne, Switzerland
5 GLO AB, Ideon Science Park, Scheelevägen 17, S-223
70 Lund, Sweden
6 GLO-USA, 1225 Bordeaux Dr, Sunnyvale, CA, 94086,
USA
Photoluminescence from GaN layers at high
temperatures as a candidate for in situ
monitoring in MOVPE
We report on the demonstration of MOVPEgrown single nanowire InGaN/GaN core-shell light
emitting diodes (LEDs) with a transparent
graphene contact for hole injection. The electrical
homogeneity of the graphene-contacted LED has
been assessed by electron beam induced current
microscopy. By comparing graphene-contacted
and metal-contacted nanowire LEDs we show that
the
contact
layout
determines
the
electroluminescence
spectrum.
The
electroluminescence changes color from green to
blue with increasing injection current. Highresolution cathodoluminescence on cleaved
nanowires allows to locate with high precision the
origin of different emitted wavelengths and
demonstrates that the blue peak originates from
the emission of the radial quantum well on the mplanes, whereas the green peak arises from the
In-rich region at the junction between the mplanes and the semipolar planes. The spectral
behavior of the electroluminescence is
understood by modeling the current distribution
within the nanowire.
C. Pralla, M. Ruebesama, C. Webera, M. Reuferb, D.
Ruetera,
a Institute of Measurement Engineering and Sensor
Technology, University of Applied Sciences Ruhr West,
PO Box 10 07 55, 45407 Muelheim a.d. Ruhr, Germany
b Institute for Natural Sciences, University of Applied
Sciences Ruhr West, PO Box 10 07 55, 45407 Muelheim
a.d. Ruhr, Germany
Journal of Crystal Growth
http://dx.doi.org/10.1016/j.jcrysgro.2014.04.001
Efficient photoluminescence (PL) spectra from
GaN and InGaN layers at temperatures up to 1100
K are observed with low noise floor and high
dynamic resolution. A number of detailed spectral
features in the PL can be directly linked to physical
properties of the epitaxial grown layer. The
method is suggested as an in situ monitoring tool
during epitaxy of nitride LED and laser structures.
Layer properties like thickness, band gap or film
temperature distribution is feasible.
Nano Letters
http://dx.doi.org/10.1021/nl5001295
InGaN/GaN core-shell single nanowire light
emitting diodes with graphene-based p-contact
Maria Tchernycheva , Pierre Lavenus , Hezhi Zhang ,
Andrey V. Babichev , Gwenole Jacopin , Mehran
Shahmohammadi , François H. Julien , Rafal Ciechonski
, Giuliano Vescovi , and Olga Kryliouk
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High-Speed Light-Emitting Diodes Emitting at 500
nm With 463-MHz Modulation Bandwidth
Liao, C.-L. ;Ho, C.-L. ; Chang, Y.-F. ; Wu, C.-H. ; Wu, M.C.
Institute of Electronics Engineering, National Tsing Hua
University, Hsinchu 30013, Taiwan
Electron Device Letters, IEEE
http://dx.doi.org/10.1109/LED.2014.2304513
Light-emitting diode (LED) is one of the most
important light sources due to its low power
consumption and long lifetime. In this letter, we
present the high-frequency characteristics of GaNbased green LEDs with different aperture
diameters. In order to get higher current density,
we use ring-shaped electrode to confine the
current injection. Unlike conventional LEDs, we
only use its natural feature to get a high
modulation bandwidth. The LEDs investigated
have a peak emission wavelength of 500 nm. The
highest optical 3-dB modulation bandwidth is
~463 MHz at 50 mA for the 500-nm green GaNbased LED with an aperture diameter of 75 μm. It
is the highest bandwidth yet reported for the
green GaN-based LEDs. The LED also exhibits a
relatively high output power of ~1.6 mW at 50 mA
as compared with other high-speed LEDs. Such
the LEDs can be applied to plastic optical fiber and
visible light communication in the future.
InxGa1−xN m-plane, c-plane, and (202¯1¯)
quantum wells. A N deficit is observed in regions
of the reconstruction generated from Ga-polar
surfaces, and the probability of detecting group-III
atoms is lower in InxGa1−xN quantum wells than
in GaN barrier layers. Despite these artifacts, the
detected In mole fraction is consistent throughout
a given quantum well regardless of the crystal
orientation of the quantum well or the
evaporation
surface
from
which
the
reconstruction was generated.
On the reliable analysis of indium mole fraction
within InxGa1−xN quantum wells using atom
probe tomography
James R. Riley1, Theeradetch Detchprohm2,a),
Christian Wetzel2 and Lincoln J. Lauhon1
1 Department of Materials Science and Engineering,
Northwestern University, Evanston, Illinois 60201, USA
2 Future Chips Constellation and Department of
Physics, Applied Physics, and Astronomy, Rensselaer
Polytechnic Institute, Troy, New York 12180, USA
Vol. 104, 152102 (2014);
http://dx.doi.org/10.1063/1.4871510
Surface crystallography and polarity are shown to
influence the detection probability of In, Ga, and
N ions during atom probe tomography analysis of
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GROUP 2 - Laser and Coherent sources
Group leader: Bruno Gayral (CEA)
Information selected by Knowmade
Numerical analysis on current and optical
confinement of III-nitride vertical-cavity surfaceemitting lasers
Ying-Yu Lai,1 Shen-Che Huang,1 Tsung-Lin Ho,1 TienChang Lu,1,* and Shing-Chung Wang1
1Department of Photonics, National Chiao Tung
University, Hsinchu 300, Taiwan
Optics Express
Vol. 22, Issue 8, pp. 9789-9797 (2014)
http://dx.doi.org/10.1364/OE.22.009789
We report on the numerical analysis of the
electrical and optical properties of currentinjected III-nitride based vertical-cavity surfaceemitting lasers (VCSELs) with three types of
current confinement schemes: the conventional
planar-indium tin oxide (ITO) type, the AlN-buried
type without ITO, and the hybrid type. The
proposed hybrid structure, which combines an ITO
layer and an intracavity AlN aperture, exhibits not
only uniform current distribution but also
enhanced lateral optical confinement. Thus, the
hybrid type design shows remarkably better
performance including lower threshold current
and series resistance compared with the planarITO type and the AlN-buried type. Furthermore,
the multi-transverse mode lasing behavior
induced by strong index guiding of the AlN
aperture is suppressed to single transverse mode
operation by reducing the aperture size. Such
design provides a powerful solution for the high
performance III-N based VCSELs and is also viable
by using current state of the art processing
techniques.
Design optimisation of metallic sub-wavelength
nanowire lasers
Sattar, Z.A. ; Shore, K.A. ; Wang, Z.
Bangor University, UK
Optoelectronics, IET
Volume: 8
Issue: 2
Date of Publication: April 2014
Page(s): 129 - 136"
http://dx.doi.org/10.1049/iet-opt.2013.0059
Design optimisation of metal-clad cylindrical
nanowire semiconductor lasers is undertaken.
Attention is focused on structures having GaN as
the material platform and utilising silver for the
metal cladding. The lasing characteristics of such
structures are explored using both the transfer
matrix method and the finite element method for
operating wavelengths from 330 to 830 nm and
for metal cladding thicknesses in the range of
5??20 nm. Specifically, calculations are performed
for the modal confinement factor, modal gain and
device length across this wide parameter space.
For representative structures, it is shown that
lower-order TE and TM mode lasing can be
supported in devices having cavity lengths of the
order of 2 and 18 μm, respectively.
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GROUP 3 - Power Electronics
Group leader: Erwan Morvan (CEA-Leti)
Information selected by Erwan Morvan (CEA-Leti)
Static and transient characteristics of GaN power
HFETs with low-conducting coating
Mikhail Gaevski1, Jianyu Deng1, Alexander
Dobrinsky1,*, Remigijus Gaska1, Michael Shur2
andGrigory Simin3
1Sensor Electronic Technology, Inc., 1195 Atlas Road,
Columbia, SC 29209, USA
2ECSE and PAPA, Rensselaer Polytechnic Institute, NY
12180, USA
3Department of Electrical Engineering, University of
South Carolina, Columbia, SC 29208, USA
Physica Status Solidi C
http://dx.doi.org/10.1002/pssc.201300541
We report on a design of GaN based HFET with a
low-conducting layer (LCL) coating. The LCL
coating dramatically improves the electric field
uniformity and increases the breakdown voltage.
A major advantage is consistent control of the
breakdown characteristics, which is expected to
dramatically improve yield and reliability. Initial
experimental studies demonstrated a three-fold
increase in the breakdown voltage compared with
conventional HFETs. The LCL also leads to a much
more uniform underlying channel depletion
evidenced by a significantly lower HFET channel
capacitance in the off state for the HFET based RF
switches. This results in a lower loss and higher
isolation. Another advantage is a faster transient
enabled by LCL, which should improve efficiency
and reduce loss for power HFET switches.
Au-Free Normally-Off AlGaN/GaN-on-Si MISHEMTs Using Combined Partially Recessed and
Fluorinated Trap-Charge Gate Structures
Huang, H. ; Liang, Y.C. ; Samudra, G.S. ; Ngo, C.L.L.
Department of Electrical and Computer Engineering,
National University of Singapore, Singapore 119260. ;
In this letter, partially recessed gate structures in
conjunction with negative trap charges by F⁻
plasma treatments both at AlGaN barrier and on
gate dielectric surface are employed to realize the
normally-OFF operation for AlGaN/GaN MetalInsulator-Semiconductor High Electron Mobility
Transistors in Au-free scheme. A partial gate
recessed trench is designed to effectively reduce
the 2-D electron gas (2DEG) density and achieve
positive threshold voltage (Vth) without severe
degradation in 2-DEG channel mobility.
Furthermore, the fixed trap charges are
innovatively placed at the gate AlGaN and S₃N₄
layers by a two-stage F⁻ plasma treatment to
further increase the Vth, without mobility
degradation. A high Vth of 1.9 V and a drain
current ~200 mA/mm are achieved in the
fabricated device, which also has a lower leakage
current and the higher breakdown voltage of
580V.
Recent advances on dielectrics technology for SiC
and GaN power devices
F. Roccafortea, P. Fiorenzaa, G. Grecoa, M. Vivonaa, R.
Lo Nigroa, F. Giannazzoa, A. Pattib, M. Saggiob
a Consiglio Nazionale delle Ricerche - Istituto per la
Microelettronica e Microsistemi (CNR-IMM) Strada VIII
5, Zona Industriale Catania 95121, Italy
b STMicroelectronics–Stradale Primosole50 Catania
95121, Italy
Applied Surface Science
Volume 301, 15 May 2014, Pages 9–18
http://dx.doi.org/10.1016/j.apsusc.2014.01.063
Silicon carbide (SiC) and gallium nitride (GaN)
devices are considered as optimal solutions to
meet the requirements of the modern power
electronics. In fact, they can allow an improved
efficiency in energy conversion at high power, as
required today in several strategic application
fields (like consumer electronics, renewable
energies technology, transportation, electric
power distribution, etc.).
However, while in the last decades impressive
progresses have been recorded both in SiC and
GaN devices, the full exploitation of these
materials has not been reached yet, due to some
open technological key issues.
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This paper reviews some recent advances in
dielectrics technology currently adopted to
optimize the performances of SiC and GaN
transistors. In particular, in the case of SiC the
discussion is focused on the optimization of
SiO2/SiC interfaces in 4H-SiC MOSFETs technology
by passivation processes of the gate oxides. On
the other hand, the current trends in dielectrics
passivation for GaN-based HEMTs to limit the gate
leakage and the current collapse are discussed.
Device characteristics of AlGaN/GaN MIS–HEMTs
with high-k HfxZr1−xO2 (x = 0.66, 0.47, 0.15)
insulator layer
Hsien-Chin Chiua, Chia-Hsuan Wua, Ji-Fan Chia, FengTso Chienb
a Dept. of Electronics Engineering, Chang Gung
University, Taoyuan, Taiwan, ROC
b Dept. of Electronics Engineering, Feng Chia
University, Taichung, Taiwan, ROC
Microelectronics Reliability
http://dx.doi.org/10.1016/j.microrel.2014.03.006
This study investigates the characteristics of
AlGaN/GaN MIS–HEMTs with HfxZr1−xO2 (x =
0.66, 0.47, and 0.15) high-k films as gate
dielectrics. Sputtered HfxZr1−xO2 with a dielectric
constant of 20–30 and a bandgap of 5.2–5.71 eV
was produced. By increasing the Zr content of
HfZrO2, the VTH shifted from −1.8 V to −1.1 V. The
highest Hf content at this study reduced the gate
leakage by approximately one order of magnitude
below that of those Zr-dominated HFETs. The
maximum IDS currents were 474 mA/mm, 542
mA/mm, and 330 mA/mm for Hf content of 66%,
47%, 15% at VGS = 3 V, respectively.
Normally-OFF Al2O3/AlGaN/GaN MOS-HEMT on
8 in. Si with Low Leakage Current and High
Breakdown Voltage (825 V)
Joseph J. Freedsman1, Takashi Egawa1, Yuya
Yamaoka2, Yoshiki Yano2, Akinori Ubukata2, Toshiya
Tabuchi2 and Koh Matsumoto3
1 Research Center for Nano-Device and System,
Nagoya Institute of Technology, Nagoya 466-8555,
Japan
2 Taiyo Nippon Sanso Corporation, Tsukuba, Ibaraki
300-2611, Japan
3 Taiyo Nippon Sanso EMC Ltd., Tama, Tokyo 206-0001,
Japan
Applied Physics Express
Vol. 7; 041003
http://dx.doi.org/10.7567/APEX.7.041003
We report recessed-gate Al2O3/AlGaN/GaN
normally-OFF metal–oxide–semiconductor highelectron-mobility transistors (MOS-HEMTs) on 8
in. Si. The MOS-HEMTs showed a maximum drain
current of 300 mA/mm with a high threshold
voltage of +2.4 V. The quite low subthreshold
leakage current (~10−8 mA/mm) yielded an
excellent ON/OFF current ratio (9 × 108) with a
small, stable subthreshold slope of 74 mV/dec. An
atomic-layer-deposited Al2O3 layer effectively
passivates, as no significant drain current
dispersions were observed. A high OFF-state
breakdown voltage of 825 V was achieved for a
device with a gate-to-drain distance of 20 µm at a
gate bias of 0 V.
Normally-off
Applications
GaN
Transistors
for
Power
O Hilt1, E Bahat-Treidel, F Brunner, A Knauer, R
Zhytnytska, P Kotara and J Wuerfl
Ferdinand-Braun-Institut, Leibniz-Institut fuer
Hoechstfrequenztechnik Gustav-Kirchhoff-Strasse 4,
12489 Berlin, Germany
Journal of Physics: Conference Series
Vol. 494; 012001
http://dx.doi.org/10.1088/1742-6596/494/1/012001
Normally-off high voltage GaN-HFETs for
switching applications are presented. Normally-off
operation with threshold voltages of 1 V and more
and with 5 V gate swing has been obtained by
using p-type GaN as gate. Different GaN-based
buffer types using doping and backside potential
barriers have been used to obtain blocking
strengths up to 1000 V. The increase of the
dynamic on-state resistance is analyzed for the
different buffer types. The best trade-off between
low dispersion and high blocking strength was
obtained for a modified carbon-doped GaN-buffer
that showed a 2.6x increase of the dynamic onstate resistance for 500 V switching as compared
to switching from 20 V off-state drain bias. Device
operation up to 200 °C ambient temperature
without any threshold voltage shift is
demonstrated.
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Material growth and device characterization of
AlGaN/GaN
single-heterostructure
and
AlGaN/GaN/AlGaN double-heterostructure field
effect transistors on Si substrates
Yu-Lin Hsiao1, Chia-Ao Chang1, Edward Yi Chang1, JerShen Maa3, Chia-Ta Chang1, Yi-Jie Wang2 and YouChen Weng3
1 Department of Materials Science and Engineering,
National Chiao-Tung University, Hsinchu, Taiwan
2 Institute of Photonic System, College of Photonics,
National Chiao-Tung University, Tainan, Taiwan
3 Institute of Lighting and Energy Photonics, College of
Photonics, National Chiao-Tung University, Tainan,
Taiwan
Vol. 7; 055501
An
Al0.2Ga0.8N/GaN/Al0.1Ga0.9N
doubleheterostructure field effect transistor (DH-FET)
structure was grown on a 150-mm-diameter Si
substrate and the crystalline quality of the
epitaxial material was found to be comparable to
that
of
an
Al0.2Ga0.8N/GaN
singleheterostructure field effect transistor (SH-FET)
structure. The fabricated DH-FET shows a lower
buffer leakage current of 9.2 × 10−5 mA/mm and
an improved off-state breakdown voltage of
higher than 200 V, whereas the SH-FET shows a
much higher buffer leakage current of 6.0 × 10−3
mA/mm and a lower breakdown voltage of 130 V.
These significant improvements show that the
Al0.2Ga0.8N/GaN/Al0.1Ga0.9N DH-FET is an
effective structure for high-power electronic
applications.
Normally-off dual gate AlGaN/GaN MISFET with
selective area-recessed floating gate
Ho-Kyun Ahna, c, Zin-Sig Kima, Sung-Bum Baea, HaeCheon Kima, Dong-Min Kanga, Sung-Il Kima, Jong-Min
Leea, Byoung-Gue Mina, Hyoung-Sup Yoona, Jong-Won
Lima, Yong-Hwan Kwona, Eun-Soo Nama, Hyung-Moo
Parkb, Hyun-Seok Kimb, Jung-Hee Leec
a Convergence Components and Materials Research
Laboratory, Electronics and Telecommunications
Research Institute, Daejeon, Republic of Korea
b The Division of Electronics and Electrical Engineering,
Dongguk University, Seoul, Republic of Korea
c The School of Electrical Engineering and Computer
Science, Kyungpook National University, Daegu,
Republic of Korea
Solid-State Electronics
Volume 95, May 2014, Pages 42–45
http://dx.doi.org/10.1016/j.sse.2014.03.005
This paper demonstrates normally-off dual gate
AlGaN/GaN MISFETs with a selective arearecessed floating gate fabricated on the
AlGaN/GaN-based heterostructure with an AlN
insertion layer. For the fabrication of the dual gate
structure, the AlGaN layer in the control gate
region was fully recessed and then an Al2O3 layer
as a gate dielectric was deposited by the atomic
layer deposition method, which ensures the
normally-off operation and greatly decreases the
leakage current. An additional floating gate with
selective area-recessed patterns, which is located
between the control gate and the drain electrode,
was employed to enhance the breakdown voltage.
The fabricated normally-off dual gate AlGaN/GaN
MISFET exhibited a threshold voltage of 2 V, a
high ION/IOFF ratio of 3 × 108 at a drain voltage of
10 V, a maximum transconductance of 88 mS/mm
at a gate voltage of 5.8 V, a drain current density
of 364 mA/mm at a gate voltage of 8 V, and a
breakdown voltage of 880 V.
GaN-on-Si Vertical Schottky and p-n Diodes
Zhang, Y. , Sun, M. ; Piedra, D. ; Azize, M. ; Zhang, X. ;
Fujishima, T. ; Palacios, T.
Microsystems Technology Laboratories, Department of
Electrical Engineering and Computer Science,
Massachusetts Institute of Technology, Cambridge, MA
02139 USA.
This letter demonstrates GaN vertical Schottky
and p-n diodes on Si substrates for the first time.
With a total GaN drift layer of only 1.5-μm thick, a
breakdown voltage (BV) of 205 V was achieved for
GaN-on-Si Schottky diodes, and a soft BV higher
than 300 V was achieved for GaN-on-Si p-n diodes
with a peak electric field of 2.9 MV/cm in GaN. A
trap-assisted space-charge-limited conduction
mechanism determined the reverse leakage and
breakdown mechanism for GaN-on-Si vertical p-n
diodes. The ON-resistance was 6 and 10 mΩ ·,cm²
for the vertical Schottky and p-n diode,
respectively. These results show the promising
KnowMade
11
performance of GaN-on-Si vertical devices for
future power applications.
Modeling of GaN-Based Normally-Off FinFET
noise measurement results also demonstrate that
the trap-density of the buffer/transition layer is
reduced by the removal of the substrate and
micromachining of the HEMTs.
Yadav, C. , Kushwaha, P. ; Khandelwal, S. ; Duarte, J.P. ;
Chauhan, Y.S. ; Hu, C.
Department of Electrical Engineering, Indian Institute
of Technology Kanpur, Kanpur 208016, India.
Isolated single-phase high power factor rectifier
using Zeta converter operating in DCM with nondissipative snubber
Callegaro, Alan D. ; ; Martins, Denizar C. ; Barbi, Ivo
Federal University of Santa Catarina EEL – INEP
In this letter, a macromodel for normally-off
(enhancement mode) AlGaN/GaN-based FinFET
(2-DEG channel at top with two MOS like sidewall
channels) is proposed. AlGaN/GaN-based FinFET
devices have improved gate control on the
channel due to additional sidewall gates
compared with planar structures, but device
characteristics
exhibit
strong
nonlinear
dependence on fin-width. The proposed model
captures both 2-DEG and sidewall channel
conduction as well as the fin-width dependency
on device characteristics. Model shows excellent
agreement with state-of-the-art experimental
data.
High Breakdown Voltage and Low Thermal Effect
Micromachined AlGaN/GaN HEMTs
Chiu, Hsien-Chin , Wang, Hsiang-Chun ; Yang, Chih-Wei
; Hsin, Yue-Ming ; Chyi, Jen-Inn ; Wu, Chang-Luen ; Wu,
Chang-Sern
Department of Electronic Engineering, Chang Gung
University, No. 259 Wen-Hwa 1st Road, Kwei-Shan,
Tao-Yuan, Taiwan, R.O.C.
Device and Materials Reliability, IEEE Transactions on
http://dx.doi.org/10.1109/TDMR.2014.2317001
This work develops a thermally stable
micromachined AlGaN/GaN high electron mobility
transistor (HEMT) with an enhanced breakdown
voltage. After removal of the Si substrate beneath
the HEMT, a 300 nm SiO2 and a 20 μm copper
layer are deposited to form the GaN-on-insulator
(G.O.I.) structure. The self-heating at high current
that is exhibited by GaN HEMTs that are by
previously developed full substrate removal
methods is eliminated. The need for complicated
substrate-transfer technology is also eliminated,
increasing chip package yield. The low frequency
Power Electronics Conference (COBEP), 2013 Brazilian
http://dx.doi.org/10.1109/COBEP.2013.6785087
This paper presents the study of a singlestage,
single-phase, unity power factor converter,
isolated by a high frequency transformer, based
on a Zeta converter operating in discontinuous
conduction mode (DCM). The main feature of the
proposed converter is its ability to naturally
emulate an apparent resistance to the ac input
source, without current sensor or current
controller. Circuit operation, theoretical analysis
and design example are included in this paper,
along with experimental results taken from a
laboratory prototype rated at 400W, input voltage
equal to 127 V, output voltage equal to 200 V,
switching frequency of 25 kHz and efficiency of
92%. In order to reduce the commutation losses
and limit the peak voltage across the power
semiconductors, a non-dissipative snubber has
been included in the laboratory prototype. With
the advent of new power semiconductor
technologies, such as SiC and GaN, power
converters operating in DCM will become very
attractive, due to their simplicity and robustness,
even for high power applications. This is the main
motivation of the study presented hereafter.
Analysis of InAl(Ga)N/GaN wet-etching by
structural, morphological and electrical methods
T Brazzini1, S Martin-Horcajo, M F Romero, Ž Gacěvić
and F Calle
Departamento de Ingeniería Electrónica and Instituto
de Sistemas Optoelectrónicos y Microtecnologías,
Universidad Politécnica de Madrid, ETSI
Telecomunicación, Av. Complutense 30, E-28040
Madrid, Spain
Semiconductor Science and Technology
Vol. 29; 075003
KnowMade
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http://dx.doi.org/10.1088/0268-1242/29/7/075003
Wet etching of InAl(Ga)N/GaN structures has
been studied in detail by means of Rutherford
backscattering spectroscopy, x-ray diffraction,
atomic force microscopy and capacitance–voltage
profiling (C–V). The samples used for the study
were grown on three different substrates
(sapphire, silicon carbide and silicon(111)). Nearly
lattice-matched compositions were measured for
all the samples. We obtained different etching
rate depending on the homogeneity and rootmean-square roughness of the surface as well as
the underlying substrate, attributing the
difference possibly to the presence of threading
dislocation in the sample. The study interest is
correlated to the possibility to control at a very
precise level the thickness etching of the material,
making it possible to fabricate normally-off
recessed gate high-electron-mobility-transistors.
developed. Based on these outcomes drain
current and transconductance are formulated
after incorporation of an appropriate Monte-Carlo
simulation based mobility model. Various nonidealities such as source–drain access resistance,
imaging charges at the interface/buffer, and
velocity saturation are taken into consideration.
The model is successful in providing accurate
description of device operation for wide range of
structural, material and dimensional parameters
as confirmed by the close agreement with
experimental data from different devices and can
be used for optimizing device performances
before fabrication.
An unified analytical model for design
consideration of doped cubic and undoped
hexagonal AlGaN/GaN MIS gate HEMTs
Saptarsi Ghosha, Ankush Baga, Sanjay K. Janaa, Partha
Mukhopadhyaya, Syed Mukulika Dinaraa, Sanjib Kabia,
Dhrubes Biswasa, b
a Advanced Technology Development Centre, Indian
Institute of Technology, Kharagpur, Khargapur 721302,
West Bengal, India
b Department of Electronics & Electrical
Communication, Indian Institute of Technology,
Kharagpur, Khargapur 721302, West Bengal, India
Solid-State Electronics
Volume 96, June 2014, Pages 1–8
http://dx.doi.org/10.1016/j.sse.2014.03.006
Physics based analytical model for predicting the
device characteristics of GaN/AlGaN metal–
insulator–semiconductor (MIS) HEMT architecture
applicable to different crystalline forms (cubic and
hexagonal) and polarity (Ga and N-polar) is
developed. Poisson’s equation is solved in the
layers and the inter-dependence of sheet density
in the 2-DEG (2 Dimensional Electron Gas), Fermi
level and gate bias is derived from the airy well
assessment
by
Schrodinger’s
equation.
Accordingly threshold voltage models are
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GROUP 4 - Advanced Electronics and RF
Group leader: Jean-Claude Dejaeger (IEMN)
Information selected by Jean-Claude Dejaeger (IEMN)
Nano-scale surface morphology optimization of
the ohmic contacts and electrical properties of
AlGaN/GaN high electron mobility transistors
using a rapid thermal annealing dielectric
protection layer
Over 3000 cm2 V−1 s−1 room temperature twodimensional electron gas mobility by annealing
Ni/Al deposited on AlGaN/GaN heterostructures
Hirokuni Tokuda, Toshikazu Kojima and Masaaki
Kuzuhara
Sung-Jin Choa, b, Cong Wanga, Nam-Young Kima,
a RFIC Research Center, Kwangwoon University,
Wolgye-dong, Nowon-Ku, Seoul, South Korea
b Electronics and Nanoscale Engineering, Glasgow
University, Glasgow, UK
Graduate School of Engineering, University of Fukui,
Fukui 910-8507, Japan
Thin Solid Films
Volume 557, 30 April 2014, Pages 262–267
http://dx.doi.org/10.1016/j.tsf.2013.11.134
Ohmic contacts with a low contact resistance and
low surface roughness are essential to ensure the
optimal device performance of AlGaN/GaN high
electron mobility transistors. A tantalum metal
layer and Si3N4 or SiO2 thin films deposited by
plasma enhanced chemical vapor deposition are
here used as an effective diffusion barrier and
protection layer, respectively, in the standard
Ti/Al/metal/Au ohmic metallization scheme to
obtain high-quality ohmic contacts. The Si3N4 or
SiO2 thickness significantly affects the surface
roughness. The optimal Ti/Al/Ta/Au ohmic contact
is prepared with a 40-nm thick Ta barrier layer
and a 50-nm thick SiO2 rapid thermal annealing
protection layer. Compared with conventional
ohmic contact stacks, the optimal contact exhibits
a low contact resistance of approximately 0.05 Ω ·
mm and a nano-scale surface roughness, with a
root-mean-square deviation of approximately 9
nm. Lastly, the ohmic contact was used to
optimize AlGaN/GaN high electron mobility
transistor with a 0.5-μm gate length, exhibiting a
maximum drain current density of 760 mA/mm, a
peak transconductance of 420 mS/mm, a unitygain cut-off frequency of 24.6 GHz, and a
maximum frequency of oscillation of 45.4 GHz.
The X-band power performance has an output
power density of 7.4 W/mm, an output power of
32 dBm, and a power added efficiency of 38% at
an input power of 21 dBm.
Vol. 7, 041001
We investigated sheet electron density (ns) and
electron
mobility
(μ)
in
AlGaN/GaN
heterostructures deposited with Ni/Al by
annealing in vacuum. We observed that both ns
and μ at room temperature increased by
annealing at 1020 K and the amount of increase
depended on the Ni/Al stack thickness. We
achieved a room temperature Hall electron
mobility of 3050 cm2 V−1 s−1, which is the highest
value
ever
reported
for
AlGaN/GaN
heterostructures. The origin of ns increase was
attributed to the additionally induced tensile
strain in AlGaN layer, which was confirmed by
Raman spectroscopy.
Characterising
thermal
resistances
and
capacitances of GaN high-electron-mobility
transistors through dynamic electrothermal
measurements
Wei, W. ; Mikkelsen, J.H. ; Jensen, O.K.
Department of Electronic Systems, Aalborg University,
Aalborg, Denmark
Microwaves, Antennas & Propagation, IET
Volume:8 , Issue: 5
April 8 2014
Page(s): 323 - 327
http://dx.doi.org/10.1049/iet-map.2013.0313
This study presents a method to characterise
thermal resistances and capacitances of GaN highelectron-mobility transistors (HEMTs) through
dynamic electrothermal measurements. A
measured relation between RF gain and the
KnowMade
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channel temperature (Tc) is formed and used for
indirect measurements of dynamic Tc responses.
Thermal resistances and capacitances are
characterised on the basis of measured Tc
responses and power dissipation (Pd) in HEMTs.
The proposed method makes it possible to
measure fast Tc responses and avoids the use of
imaging
and
spectroscopy
techniques.
Additionally, the proposed method ensures that
trapping effects have insignificant impact on the
measurements of Tc responses, which makes this
method suitable for GaN HEMT characterisation.
The applicability of this method is demonstrated
by characterising thermal resistances and
capacitances of a CREE CGH40006P GaN HEMT.
Position of fermi level on Al0.2Ga0.8N surface
and
distribution
of
electric
field
in
Al0.2Ga0.8N/GaN heterostructures without and
with AlN layer
M. Gladysiewicz1,a), L. Janicki1, R. Kudrawiec1, J.
Misiewicz1, M. Wosko2, R. Paszkiewicz2, B.
Paszkiewicz2 and M. Tłaczała2
1 Institute of Physics, Wroclaw University of
Technology, Wybrzeze Wyspianskiego 27, 50-370
Wroclaw, Poland
2 The Faculty of Microsystem Electronics and Photonic,
Wroclaw University of Technology, Janiszewskiego
11/17, 50-372 Wroclaw, Poland
Vol. 115, 133504 (2014);
http://dx.doi.org/10.1063/1.4870442
Position of Fermi level on Al0.2Ga0.8N surface
and
distribution
of
electric
field
in
Al0.2Ga0.8N/GaN transistor heterostructures
without and with AlN layer were studied
experimentally
using
contactless
electroreflectance and theoretically solving
Schrodinger-Poisson equation with various
surface boundary conditions. It has been observed
that the thin AlN layer changes very strongly the
distribution of electric field in this heterostructure
but the Fermi level position on Al0.2Ga0.8N
surface does not change significantly. Its position
is the same within experimental uncertainly (i.e.,
∼0.5 eV below conduction band) for both bulk
Al0.2Ga0.8N
and
Al0.2Ga0.8N/GaN
heterostructures.
Bistability Characteristics of GaN/AlN Resonant
Tunneling Diodes Caused by Intersubband
Transition and Electron Accumulation in
Quantum Well
Nagase, M. ; Tokizaki, T.
National Institute of Advanced Industrial Science and
Technology, Tsukuba 305-8568, Japan.
Electron Devices, IEEE Transactions on
http://dx.doi.org/10.1109/TED.2014.2310473
The bistability characteristics of GaN/AlN resonant
tunneling diodes (RTDs) grown on a sapphire
substrate were investigated. The RTDs exhibit
bistability characteristics with high and low
resistivity switched by varying the polarity of the
bias voltage. Negative differential resistance is
realized
in
the
current--voltage
(I-V)
characteristics after low resistivity is achieved by
application of a negative bias. The calculated I-V
characteristics based on self-consistent methods
indicate that the bistability characteristics are
caused by the accumulation of electrons in the
quantum well due to intersubband transitions.
Also, the bistability characteristics of GaN/AlN
RTDs were discussed toward the application to
the ultrafast nonvolatile memory.
Epitaxial growth of ultra-thin NbN films on
AlxGa1−xN buffer-layers
S Krause1, D Meledin1, V Desmaris1, A Pavolotsky1, V
Belitsky1, M Rudziński2 and E Pippel3
1 Group for Advanced Receiver Development,
Chalmers University of Technology, SE-412 96
Gothenburg, Sweden
2 Institute of Electronic Materials Technology (ITME),
01-919 Warsaw, Poland
3 Max Planck Institute of Microstructure Physics, D06120 Halle/Saale, Germany
Superconductor Science and Technology
Vol. 27; 065009
http://dx.doi.org/10.1088/0953-2048/27/6/065009
The suitability of AlxGa1−xN epilayers to deposit
onto ultra-thin NbN films has been demonstrated
for the first time. High quality single-crystal films
with 5 nm thickness confirmed by high resolution
transmission electron microscopy (HRTEM) have
been deposited in a reproducible manner by
means of reactive DC magnetron sputtering at
elevated temperatures and exhibit critical
KnowMade
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temperatures (Tc) as high as 13.2 K and residual
resistivity ratio (RRR) ~1 on hexagonal GaN
epilayers. On increasing the Al content x in the
AlxGa1−xN epilayer above 20%, a gradual
deterioration of Tc to 10 K was observed.
Deposition of NbN on bare silicon substrates
served as a reference and comparison. Excellent
spatial homogeneity of the fabricated films was
confirmed by R(T) measurements of patterned
micro-bridges across the entire film area. The
superconducting properties of these films were
further characterized by critical magnetic field and
critical current measurements. It is expected that
the employment of GaN material as a buffer-layer
for the deposition of ultra-thin NbN films will
prospectively benefit terahertz electronics,
particularly hot electron bolometer (HEB) mixers.
Fabrication of p-channel heterostructure field
effect transistors with polarization-induced twodimensional hole gases at metal–polar
GaN/AlInGaN interfaces
B Reuters1,3, H Hahn1,3, A Pooth1,3, B Holländer2,3, U
Breuer4, M Heuken1,5, H Kalisch1,3 and A Vescan1,3
1 RWTH Aachen University, GaN Device Technology,
Sommerfeldstrasse 24, 52074 Aachen, Germany
2 Forschungszentrum Jülich GmbH, PGI9-IT, 52425
Jülich, Germany
3 JARA-Fundamentals of Future Information
Technologies, 52425 Jülich, Germany
4 Forschungszentrum Jülich GmbH, ZEA-3, 52425 Jülich,
Germany
5 AIXTRON SE, Kaiserstr. 98, 52134 Herzogenrath,
Germany
Journal of Physics D: Applied Physics
Vol. 47; 175103
http://dx.doi.org/10.1088/0022-3727/47/17/175103
Novel nitride-based heterostructures have been
fabricated demonstrating two-dimensional hole
gases as the basis for p-channel transistors. The
carrier density in the 2DHG is adjusted between
very high values of 2 × 1013 cm−2 and low values
of 6 × 1011 cm−2 by the polarization difference,
ΔP, between quaternary AlInGaN backbarriers and
a GaN channel on top. Record mobilities for holes
in GaN of 43 cm2 V−1 s−1 (median 30 cm2 V−1
s−1) are observed for a moderate 2DHG density of
1.3 × 1012 cm−2 (median 2.2 × 1012 cm−2).
Heterostructures with different backbarrier
compositions are processed to field effect
transistors and show a systematic threshold
voltage shift from positive to negative values
according to the corresponding 2DHG density. It is
shown for the first time that by appropriate
polarization-engineering through changing the
AlInGaN composition, both depletion and
enhancement mode behaviour can be achieved
for p-channel devices.
Drain current densities |Id| above 40 mA mm−1
at a drain source voltage Vds of −10 V are
achieved for heterostructures with high
polarization differences, ΔP, between AlInGaN
backbarrier and GaN channel. Reducing ΔP leads
to decreasing on-state drain currents |Id| with a
simultaneous reduction in off-state current. This
results in very large on/off ratios of up to 108 for
enhancement mode devices, demonstrating
record performances and great potential for
future applications.
Trapping
in
GaN-based
metal-insulatorsemiconductor transistors: Role of high drain
bias and hot electrons
M. Meneghini1,a), D. Bisi1, D. Marcon2, S. Stoffels2, M.
Van Hove2, T.-L. Wu2, S. Decoutere2, G. Meneghesso1
and E. Zanoni1
1 Department of Information Engineering, University of
Padova, via Gradenigo 6/B, 35131 Padova, Italy
2 IMEC, Kapeldreef 75, 3001 Heverlee, Belgium
Vol. 104, 143505 (2014);
http://dx.doi.org/10.1063/1.4869680
This paper describes an extensive analysis of the
role of off-state and semi-on state bias in inducing
the trapping in GaN-based power High Electron
Mobility Transistors. The study is based on
combined pulsed characterization and onresistance
transient
measurements.
We
demonstrate that—by changing the quiescent bias
point from the off-state to the semi-on state—it is
possible to separately analyze two relevant
trapping mechanisms: (i) the trapping of electrons
in the gate-drain access region, activated by the
exposure to high drain bias in the off-state; (ii) the
trapping of hot-electrons within the AlGaN barrier
or the gate insulator, which occurs when the
devices are operated in the semi-on state. The
KnowMade
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dependence of these two mechanisms on the bias
conditions and on temperature, and the
properties (activation energy and cross section) of
the related traps are described in the text.
New degradation mechanism observed for
AlGaN/GaN HEMTs with sub 100 nm scale
unpassivated regions around the gate periphery
Ponky Ivoa, Eunjung Melanie Choa, Przemyslaw
Kotaraa, Lars Schellhasea, Richard Lossya, Ute Zeimera,
Anna Mogilatenkoa, Joachim Würfla, Günther Tränklea,
Arkadiusz Glowackib, Christian Boitb
a Ferdinand-Braun-Institut, Leibniz-Institut für
Höchstfrequenztechnik, Gustav-Kirchhoff-Strasse 4,
12489 Berlin, Germany
b Halbleiterbauelemente Technische Universität Berlin,
Einsteinufer 19, 10589 Berlin, Germany
Microelectronics Reliability
http://dx.doi.org/10.1016/j.microrel.2014.03.005
AlGaN/GaN HEMTs with low gate leakage current
in the μA/mm range have been fabricated with a
small-unpassivated region close to the gate foot.
They showed considerably higher critical voltage
values (average VCR = 60 V) if subjected to step
stress testing at OFF-state conditions and room
temperature as compared to standard devices
with conventional gate technology. This is due to
the fact that electrons injected from the gate can
be accumulated at the unpassivated region and
thus builds up negative charge. The lower gate
leakage is due to virtual gate formation, which is
reducing local electric field in the vicinity of the
gate. In contrast to devices with standard gate
technology, degradation during step stressing is
not associated with a simultaneous gate leakage
and drain leakage current increase but with a
strong increase of drain current at OFF-state
conditions while the gate leakage is practically not
affected. Then a relatively higher critical voltage
of around 60 V is achieved. An abrupt increase of
subthreshold drain current implies the formation
of a conductive channel bypassing the gate region
without influencing gate leakage. It is believed
that hopping conductivity via point defects
formed during device stressing creates this
channel. Once this degradation mode takes place,
the drain current of affected devices significantly
drops. This can be explained by negative trap
formation in the channel region affecting the total
charge
balance
in
2DEG
region.
Electroluminescence measurements on both fresh
and degraded devices showed no hot spots at
OFF-state conditions. However, there is additional
emission at ON-state bias, which suggests
additional energetic states that lead to radiative
electron transition effects in the degraded
devices, most possibly defect states in the buffer.
AlGaN/GaN HEMT structures on ammono bulk
GaN substrate
P Kruszewski1,2, P Prystawko1,2, I Kasalynas3, A
Nowakowska-Siwinska2, M Krysko1, J Plesiewicz2, J
Smalc-Koziorowska1,2, R Dwilinski4, M Zajac4, R
Kucharski4 and M Leszczynski1,2
1 Institute of High Pressure Physics UNIPRESS, ul
Sokołowska 29/37, 01-142 Warsaw, Poland
2 Top-GaN Sp.z o.o., ul Sokołowska 29/37, 01-142
Warsaw, Poland
3 Center for Physical Science and Technology, A
Goštauto 11, LT-01108 Vilnius, Lithuania
4 Ammono SA, ul Prusa 2, 00-493 Warsaw, Poland
Vol. 29; 075004
http://dx.doi.org/10.1088/0268-1242/29/7/075004
The work shows a successful fabrication of
AlGaN/GaN high electron mobility transistor
(HEMT) structures on the bulk GaN substrate
grown by ammonothermal method providing an
ultralow dislocation density of 104 cm−2 and
wafers of size up to 2 inches in diameter. The
AlGaN layers grown by metalorganic chemical
vapor phase epitaxy method demonstrate
atomically smooth surface, flat interfaces with
reproduced low dislocation density as in the
substrate. The test electronic devices—Schottky
diodes and transistors—were designed without
surface passivation and were successfully
fabricated
using
mask-less
laser-based
photolithography procedures. The Schottky
barrier devices demonstrate exceptionally low
reverse currents smaller by a few orders of
magnitude in comparison to the Schottky diodes
made of AlGaN/GaN HEMT on sapphire substrate
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Characterization of GaN-based p-channel device
structures at elevated temperatures
Herwig Hahn, Benjamin Reuters, Alexander Pooth1,
Holger Kalisch and Andrei Vescan
1 A Pooth is now with the Center for Device
Thermography and Reliability, University of Bristol, BS8
1TL Bristol, UK.
Vol. 29; 075002
http://dx.doi.org/10.1088/0268-1242/29/7/075002
The interest in GaN for logic applications is
increasing.
With
complementary
logic
architectures requiring the lowest power
consumption, the need for GaN-based p-channel
transistors is growing. Yet, the knowledge and the
maturity of p-channel devices is far behind those
of their n-channel counterparts. By analysing pchannel transistors with a high on/off ratio and a
low subthreshold swing under elevated
temperatures, we attempt to improve this
situation. This is the first report on transistor
operation at temperatures as high as 175 °C.
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GROUP 5 - Sensors and MEMS
Group leader: Marc Faucher (IEMN)
Information selected by Paul Leclaire (CRHEA-CNRS)
Enhanced AlN nanostructures for pyroelectric
sensors
E. Crisman1, A. Drehman2,†, R. Miller3, A. Osinsky3, D.
Volovik3 andV. Vasilyev4,*
1Department of Chemical Engineering, University of
Rhode Island, Kingston, RI 02881, USA
2Air Force Research Laboratory, USA
3Agnitron Technology, Inc., Eden Prairie, MN 55344,
USA
4Air Force Research Laboratory, Wright-Patterson Air
Force Base, OH 45433, USA
Measurements of the pyroelectric coefficient and
pyroelectric voltage response of polycrystalline
AlN films are presented. The results were used to
calculate pyroelectric detectivity figures of merit
in order to compare potential AlN pyroelectric
sensor performance to other pyroelectric
materials such as epitaxial AlN, PbSc0.5Ta0.5O3,
and Ba0.65Sr0.35TiO3 films. We observed
substantial enhancement (∼5x) of pyroelectric
coefficient and pyroelectric figure of merit in
polycrystalline multi-oriented AlN films when
compared to epitaxial monocrystalline AlN films. A
mechanism
of
such
augmentation
in
polycrystalline AlN films is proposed and
discussed. Despite the relatively small absolute
value of pyroelectric coefficient, AlN presents
pyroelectric detectivity figure of merit near the
same magnitude as commonly used pyroelectric
materials because of its relatively low dielectric
constant. The low dielectric constant enables high
speed sensor operation >MHz. The results of
these studies are suggesting even higher
pyroelectric response might be obtainable for the
polycrystalline thin film AlN structures.
Microelectromechanical Systems, Journal of
http://dx.doi.org/10.1109/JMEMS.2014.2308544
We present a method for attenuating the spurious
responses in aluminum nitride micromechanical
filters and demonstrate the technique in a 4-pole
self-coupled filter operating at 494 MHz. In the
standard implementation of a 4-pole self-coupled
filter, each filter pole is realized using physically
identical resonators. The spur mitigation approach
reported here realizes the four poles of the filter
using two different physical implementations of
the resonator. Both resonators are designed to
have identical responses at the desired resonant
frequency of 494 MHz, while many of the spurious
responses of the two resonators appear at
nonidentical frequencies and do not add
constructively at the filter output. Using the
reported method, the measured attenuation of
the largest filter spur is increased by 47.5 dB when
compared with a 4-pole filter realized using
identical resonators (standard approach) to form
each filter pole. The filter realized using the
reported spur attenuation approach has $>$59.6
dBc of stopband and spurious response rejection
over nearly a 2-GHz frequency span. [2013-0342]
Piezoelectric Ultrasonic Transducer Based on
Flexible AlN
Vincenzo Mariano Mastronardia, c, Francesco Guidoa,
b, Massimiliano Amatoa, b, Massimo De Vittorioa, b,
Simona Petronia
a Center for Biomolecular Nanotechnologies @UNILE,
Istituto Italiano di Tecnologia, via Barsanti, 73010,
Arnesano (LE), Italy
b Dip. Ingegneria dell’Innovazione of Università del
Salento, via per Monteroni, 73100, Lecce, Italy
c Dip. Scienza Applicata e Tecnologia, Corso Duca degli
Abruzzi, 10129, Torino, Italy
A Method for Attenuating the Spurious
Responses of Aluminum Nitride Micromechanical
Filters
Microelectronic Engineering
http://dx.doi.org/10.1016/j.mee.2014.03.034
Olsson, R.H. ;Nguyen, J. ; Pluym, T. ; Hietala, V.M.
MEMS Technologies, Sandia National Laboratories,
Albuquerque, NM 87185 USA.
This work presents a promising ultrasound
wearable technology based on a piezoelectric
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transducer, realized on flexible highly oriented
Aluminum Nitride, with significant mechanical
displacement in spite of being attached on a rigid
support. Circular membranes with different radius
sizes, based on 1-μm-thick AlN thin film as the
active piezoelectric layer, are designed,
fabricated, and characterized. The AlN is
deposited on kapton HN substrate with a low
sputtering deposition temperature that allows the
integration and the compatibility with flexible
electronics. Mechanical and thermal stability of
kapton makes this polyimide based sheet a
potential substrate for flexible piezoelectric thin
film technology. The actuation at low voltage (110V) of the AlN membranes is studied in air in the
range of ultrasound frequencies, from 0Hz up to
2MHz; the voltage amplitude, the shape and
displacement of the flexure mode (0, 1) is studied
by a Laser Doppler Vibrometer to characterize the
mechanical properties of the device.
AlN/GaN/AlN heterostructures grown on Si
substrate by plasma-assisted MBE for MSM UV
photodetector applications
M.Z. Mohd Yusoffa, b, A. Mahyuddinc, Z. Hassanb, H.
Abu Hassanb, M.J. Abdullahb, M. Rusopd, S.M.
Mohammadb, Naser M. Ahmedb
a Department of Applied Sciences, Universiti Teknologi
MARA (Pulau Pinang), 13500 Permatang Pauh, Penang,
Malaysia
b Nano-Optoelectronics Research and Technology
Laboratory, School of Physics, Universiti Sains Malaysia,
11800 Penang, Malaysia
c Universiti Kuala Lumpur, Malaysian Institute of
Industrial Technology (MITEC), Persiaran Sinaran Ilmu,
Bandar Seri Alam, 81750 Johor, Malaysia
d Faculty of Electrical Engineering, Universiti Teknologi
MARA, 40450 Shah Alam, Malaysia
Materials Science in Semiconductor Processing
http://dx.doi.org/10.1016/j.mssp.2014.03.041
The
AlN/GaN/AlN
heterostructures
were
successfully grown on silicon substrate by plasmaassisted molecular beam epitaxy (MBE). High
purity gallium (7N) and aluminum (6N5) were
used to grow GaN and AlN, respectively. The
structural and optical properties of the samples
have been investigated by high-resolution X-ray
diffraction (HR-XRD), photoluminescence (PL),
Raman spectroscopy, transmission electron
microscopy (TEM), selected area electron
diffraction
(SAED),
dark
field
scanning
transmission electron microscopy (DF STEM), and
high-angle annular dark field scanning
transmission electron microscopy (HAADF STEM).
HR-XRD measurement showed that the sample
has a typical diffraction pattern of hexagonal
AlN/GaN/AlN heterostructures. Raman spectra
revealed all four Raman-active modes, i.e., GaNlike E2 (H), AlN-like A1 (TO), AlN-like E2 (H), and
AlN-like A1 (LO) inside the AlN/GaN/AlN
heterostructures. Good thickness uniformity of
the layers and high-quality hetero-structures
without cracking were confirmed by TEM, SAED,
DF STEM and HAADF STEM. The fabricated
AlN/GaN/AlN heterostructures based metalsemiconductor-metal (MSM) for the UV
photodetector shows a rise and fall of
photoresponses, suggesting that the AlN/GaN/AlN
heterostructures have good carrier transport and
crystallinity properties.
Suspended membrane
refractive index sensing
GaN
gratings
for
Yongjin Wang1, Jiajia Chen1, Zheng Shi1, Shumin He1,
Martin Lopez Garcia2, Lifeng Chen3, Nikolai A.
Hueting3, Martin Cryan3, Miao Zhang4 and Hongbo
Zhu1
1 Grüenberg Research Centre, Nanjing University of
Posts and Telecommunications, Nanjing 210003, China
2 Bristol Centre for Nanoscience and Quantum
Information (NSQI), University of Bristol, Bristol BS8
1TH, U.K.
3 Department of Electrical and Electronic Engineering,
University of Bristol, Bristol BS8 1TH, U.K.
4 State Key Laboratory of Functional Materials for
Informatics, Institute of Microsystem and Information
Technology, Chinese Academy of Sciences, Shanghai
200050, China
Vol.7; 052201
In this paper, we describe the fabrication and the
novel procedure for back thinning the GaN layer,
which leads to improved optical performance.
Angular-resolved reflectance measurements are
then conducted to characterize the GaN gratings
and show the dependence of resonant
wavelength on grating period and membrane
thickness. The measured results compare well
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with electromagnetic modeling based on rigorous
coupled wave analysis (RCWA). Altering the
dielectric environment has been shown as a novel
sensing mechanism, and this work opens the way
to the fabrication of novel GaN resonant photonic
devices for refractive index sensing applications in
the visible wavelength range.
The effect of charge layer separating absorption
and multiplication on the performance of GaN
avalanche photodiodes
Jingjing Wanyan, Zhaoqi Sun, Shiwei Shi, Gang He,
Mingzai Wu, Guang Li
School of Physics and Materials Science, Anhui
University, Hefei 230039, People‫׳‬s Republic of China
Solid State Communications
Volume 189, July 2014, Pages 28–31
http://dx.doi.org/10.1016/j.ssc.2014.03.009
The photo-response characteristics of a backilluminated avalanche photodiode are studied
theoretically by using a charge layer to separate
the absorption and multiplication regions. The
results show that the average electric field at the
breakdown voltage is approximately 3.0 MV/cm,
close to the reported value, in good agreement
with that of the experiments. Multiplication gain
has been calculated as a function of charge layer
thickness and doping concentration. A maximum
optimal gain of 7×104 is obtained with the doping
concentration of 2×1018 cm−3. The temperature
dependence of avalanche voltage shows a large
positive coefficient of 0.15 V/K, confirming that
the avalanche multiplication is the dominant gain
mechanism in the photodiodes.
GaN nanowires for piezoelectric generators
Noelle Gogneau1,*, Pascal Chrétien2, Elisabeth
Galopin1,3, Stephane Guilet1, Laurent Travers1, JeanChristophe Harmand1 andFrédéric Houzé2
1Laboratoire de Photonique et de Nanostructures,
CNRS-LPN-UPR20, Route de Nozay, 91460 Marcoussis,
France
2Laboratoire de Génie Electrique de Paris, UMR CNRSSupélec 8507, Universités Pierre et Marie Curie et
Paris-Sud, 11 rue Joliot-Curie, 91192 Gif sur Yvette,
France
3Present address: Institute d'Electronique, de
Microelectronique et de Nanotechnologie, Avenue
Poincaré, 59652 Villeneuve d'Ascq, France
Physica Status Solidi (RRL) - Rapid Research Letters
http://dx.doi.org/10.1002/pssr.201409105
We demonstrate the high potential of GaN
nanowires (NWs) to convert mechanical energy
into electric energy. Using an atomic force
microscope equipped with a Resiscope module,
an average output voltage of –74 mV and a
maximum of –443 mV ± 2% per NW were
measured. This latter value is the highest reported
so far for GaN NWs. By considering these output
signals, we have estimated an average and a
maximum power density generated by one layer
of GaN NWs of the order of 5.9 mW/cm2 and 130
mW/cm2, respectively. These results offer
promising prospects for the use of GaN NWs for
high-efficiency ultracompact piezogenerators.
Comparative study of Schottky diode type
hydrogen sensors based on a honeycomb GaN
nanonetwork and on a planar GaN film
Aihua Zhong, Takashi Sasaki, Kazuhiro Hane
Department of Nanomechanics, Tohoku University,
Sendai 980-8579, Japan
International Journal of Hydrogen Energy
http://dx.doi.org/10.1016/j.ijhydene.2014.03.120
We demonstrate Schottky diode type hydrogen
(H2) sensors both on a planar GaN film grown by
Metal Organic Chemical Vapor Deposition and on
a honeycomb GaN nanonetwork grown by
Molecular
Beam
Epitaxy.
The
metalsemiconductor Pt/planar GaN film Schottky diode
was fabricated and used as a H2 sensor element
with response time τ of 80 s (10,000 ppm) and
2000 ppm limit of detection for hydrogen gas
(LODH2) at 373 K. A significant improvement in H2
detection is observed for the honeycomb GaN
nanonetwork. The characteristics of the H2 sensor
on the honeycomb GaN nanonetwork are
quantitatively studied in comparison with that on
the planar GaN film. The response time τ is
shortened by a factor of 27 (3 s versus 80 s) and
the LODH2 is lowered by two orders of
magnitude, from 2000 to 50 ppm. Moreover, the
operating temperature could be reduced to room
temperature. Through analyzing the transientstate, we observed a reduction of activation
energy Ea from 6.22 to 2.4 kcal/mol. The reduced
activation energyEa is regarded as the reason that
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leads to a superior H2 detection of the
honeycomb GaN nanonetwork in terms of
response time τ and operating temperature.
Performance comparison of front- and backilluminated modes of the AlGaN-based p-i-n
solar-blind ultraviolet photodetectors
Xiaojing Li1, Degang Zhao1,a), Desheng Jiang1,
Zongshun Liu1, Ping Chen1, Lingcong Le1, Jing Yang1,
Xiaoguang He1, Shuming Zhang2, Jianjun Zhu2, Hui
Wang2, Baoshun Zhang2, Jianping Liu2 and Hui Yang2
1 State Key Laboratory on Integrated Optoelectronics,
Institute of Semiconductors, Chinese Academy of
Science, PO Box 912, Beijing 100083, China
2 Suzhou Institute of Nano-tech and Nano-bionics,
Chinese Academy of Sciences, Suzhou 215123, China
Journal of Vacuum Science & Technology B
Vol. 32, 031204 (2014)
http://dx.doi.org/10.1116/1.4871460
The authors report the comparison of front- and
back-illuminated mode operations of Al0.4Ga0.6N
positive-intrinsic-negative
solar-blind
photodetectors (PDs) grown on the double-side
polished sapphire substrates by metalorganic
chemical vapor deposition. It is shown that the
responsivity in back-illumination mode of
fabricated PDs can be almost three times as that
in front-illumination mode under the same
reverse bias. In addition, a wide spectral response
between 300 nm and 370 nm is observed, which is
not expected for solar-blind PDs in both
illumination modes, while the PDs in backillumination mode have a stronger ability to
restrain the long-wavelength response, showing
larger solar-blind/ultraviolet rejection ratio than
front-illumination mode. The reasons for the
performance differences are discussed.
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GROUP 6 - Photovoltaics and Energy harvesting
Group leader: Eva Monroy (INAC-CEA)
A Hybrid Resonant Converter Utilizing a
Bidirectional GaN AC Switch for High-Efficiency
PV Applications
Labella, T. ; Lai, J.-S.J.
Future Energy Electronics Center, Virginia Tech,
Blacksburg, VA 24061 USA
Industry Applications, IEEE Transactions on
http://dx.doi.org/10.1109/TIA.2014.2312818
This paper introduces a novel isolated hybrid
resonant converter with smooth transition
between multiple operating modes. With the
simple addition of a bidirectional ac switch, the
highly-efficient
series resonant
converter
operating in the discontinuous conduction mode
(DCM) is combined with a phase-shifted fullbridge buck converter and a pulse width
modulated (PWM) boost converter in order to
provide high power conversion efficiency over a
wide input-voltage operating range utilizing a
simple topology and simple control techniques.
First, the topology is introduced and the
converter’s operating modes are discussed. Next,
closed-loop input-voltage controllers are designed
for the different operating modes and a smooth
transition technique is introduced using a twocarrier modulation scheme. Experimental results
are provided to verify the proposed system using
a 300-W prototype that achieved a 97.5%
California Energy Commission (CEC) weighted
efficiency with a 30-V input including all auxiliary
and control losses.
Improved efficiency and stability of GaN
photoanode in photoelectrochemical water
splitting by NiO cocatalyst
Soo Hee Kim, Mohamed Ebaid, Jin-Ho Kang, Sang-Wan
Ryu
Department of Physics, Chonnam National University,
Gwangju, 500-757, Korea
The NiO cocatalyst was deposited on a GaN
photoanode to improve the water splitting
efficiency and to stabilize the photoelectrolysis of
the GaN photoanode without corrosion of the
GaN layer. The photoanode performance was
investigated for various NiO deposition conditions
based on metal organic decomposition. The GaN
photoanode with the optimized NiO morphology
showed significantly improved efficiency and
photocurrent stability during water splitting
compared to the reference GaN. No corrosion was
observed for the GaN photoanode combined with
NiO, which confirmed that the enhanced stability
was related to the suppressed GaN etching at the
surface.
The
improved
water
splitting
performance was attributed to the fast transport
of photo-generated holes in the valence band
from GaN to NiO and the efficient water reduction
at the NiO/electrolyte interface.
Simulation analysis of GaN microdomes with
broadband omnidirectional antireflection for
concentrator photovoltaics
Lu Han1 and Hongping Zhao1
1 Department of Electrical Engineering and Computer
Science, Case Western Reserve University, Cleveland,
Ohio 44106, USA
Vol. 115, 133102 (2014);
http://dx.doi.org/10.1063/1.4870714
Microdome structures are analyzed as surface
topology to reduce surface reflection over a broad
spectral range and wide light incidence angle for
concentrator photovoltaics application. Three
dimensional finite difference time domain method
was used to accurately calculate the surface
reflection and transmission for surface topologies
with different feature sizes and aspect ratios.
Studies show that the use of GaN microdomes will
lead to a significant reduction of the surface
reflection over a broad wavelength range and
wide incidence angle range. The surface reflection
significantly depends on the surface structure
feature size and geometrical shape. The design of
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the GaN microdomes provides flexibility to tune
the structure in order to obtain the minimum
surface reflection for different designs of
concentrator optical systems. The surface
reflections of the GaN microdomes are compared
with that of the conventional flat surface as well
as the one with antireflection coating.
Realizing
InGaN
photoelectrochemical
photosynthesis
monolithic
cells
for
solarartificial
R. Dahal1,a), B. N. Pantha1,b), J. Li1, J. Y. Lin1 and H. X.
Jiang1,c)
1 Department of Electrical and Computer Engineering,
Texas Tech University, Lubbock, Texas 79409, USA
Vol. 104, 143901 (2014);
http://dx.doi.org/10.1063/1.4871105
InGaN alloys are very promising for solar water
splitting because they have direct bandgaps that
cover almost the whole solar spectrum. The
demonstration of direct solar-to-fuel conversion
without external bias with the sunlight being the
only energy input would pave the way for realizing
photoelectrochemical (PEC) production of
hydrogen by using InGaN. A monolithic solar-PEC
cell based on InGaN/GaN multiple quantum wells
capable to directly generate hydrogen gas under
zero bias via solar water splitting is reported.
Under the irradiation by a simulated sunlight (1sun with 100 mW/cm2), a 1.5% solar-to-fuel
conversion efficiency has been achieved under
zero bias, setting a fresh benchmark of employing
III-nitrides for artificial photosynthesis. Time
dependent hydrogen gas production photocurrent
measured over a prolonged period (measured for
7 days) revealed an excellent chemical stability of
InGaN in aqueous solution of hydrobromic acid.
The results provide insights into the architecture
design of using InGaN for artificial photosynthesis
to provide usable clean fuel (hydrogen gas) with
the sunlight being the only energy input.
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GROUP 7 - Materials, Technology and Fundamental
Group leader: Jean-Christophe Harmand (LPN-CNRS)
NANO
III-nitride nanowire based light emitting diodes
on carbon paper
Michael A. Mastro1,*, Travis J. Anderson1, Marko J.
Tadjer1, Francis J. Kub1, Jennifer K. Hite1, Jihyun Kim2
andCharles R. Eddy Jr.1
1US Naval Research Laboratory, 4555 Overlook Ave.
SW, Washington, DC 20375, USA
2Department of Chemical and Biological Engineering,
Korea University, Seoul, South Korea
This article presents the use of flexible carbon
substrates for the growth of III-nitride nanowire
light emitters. A dense packing of gallium nitride
nanowires were grown on a carbon paper
substrate. The nanowires grew predominantly
along the a-plane direction, normal to the local
surface of the carbon paper. Strong photo- and
electro-luminescence was observed from InGaN
quantum well light emitting diode nanowires.
Reducing the efficiency droop by lateral carrier
confinement in InGaN/GaN quantum-well
nanorods
Chentian Shi,1 Chunfeng Zhang,1,* Fan Yang,1 Min Joo
Park,2 Joon Seop Kwak,2,5 Sukkoo Jung,3 Yoon-Ho
Choi,3 Xiaoyong Wang,1 and Min Xiao1,4,6
1National Laboratory of Solid State Microstructures
and Department of Physics, Nanjing University, Nanjing
210093, China
2Department of Printed Electronics Engineering,
Sunchon National University, Sunchon, Jeonnam 540742, South Korea
3Emerging Technology Laboratory, LG Electronics
Advanced Research Institute, Seoul 137-724, South
Korea
4Department of Physics, University of Arkansas,
Fayetteville, Arkansas 72701, USA
Optics Express
Vol. 22, Issue S3, pp. A790-A799 (2014)
Efficiency droop is a major obstacle facing highpower application of InGaN/GaN quantum-well
(QW) light-emitting diodes (LEDs). In this paper,
we report the suppression of efficiency droop
induced by the process of density-activated defect
recombination in nanorod structures of a-plane
InGaN/GaN QWs. In the high carrier density
regime, the retained emission efficiency in a dryetched nanorod sample is observed to be over
two times higher than that in its parent QW
sample. We further argue that such improvement
is a net effect that the lateral carrier confinement
overcomes the increased surface trapping
introduced during fabrication.
Improvement
of
electroluminescence
performance by integration of ZnO nanowires
and single-crystalline films on ZnO/GaN
heterojunction
Zhifeng Shi1, Yuantao Zhang1,a), Xijun Cui1, Bin Wu1,
Shiwei Zhuang1, Fan Yang1, Xiaotian Yang2, Baolin
Zhang1 and Guotong Du1
1 State Key Laboratory on Integrated Optoelectronics,
College of Electronic Science and Engineering, Jilin
University, Qianjin Street 2699, Changchun 130012,
China
2 School of Electrical and Electronic Information, Jilin
Institute of Architecture and Civil Engineering,
Changchun 130118, China
Vol. 104, 131109 (2014);
http://dx.doi.org/10.1063/1.4870517
Heterojunction light-emitting diodes based on nZnO nanowires/ZnO single-crystalline films/p-GaN
structure have been demonstrated for an
improved electroluminescence performance. A
highly efficient ultraviolet emission was observed
under forward bias. Compared with conventional
n-ZnO/p-GaN structure, high internal quantum
efficiency and light extraction efficiency were
simultaneously considered in the proposed diode.
In addition, the diode can work continuously for
∼10 h with only a slight degradation in harsh
environments, indicating its good reliability and
application prospect in the future. This route
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opens possibilities for the development of
advanced nanoscale devices in which the
advantages of ZnO single-crystalline films and
nanostructures can be integrated together.
Efficiency improvement of a vertical lightemitting diode through surface plasmon coupling
and grating scattering
Chun-Han Lin,1 Chieh Hsieh,1 Charng-Gan Tu,1 Yang
Kuo,1,2 Horng-Shyang Chen,1 Pei-Ying Shih,1 Che-Hao
Liao,1 Yean-Woei Kiang,1,3 C. C. Yang,1,3,* Chih-Han
Lai,4 Guan-Ru He,4 Jui-Hung Yeh,4 and Ta-Cheng Hsu4
1Institute of Photonics and Optoelectronics, National
Taiwan University, 1, Roosevelt Road, Section 4, Taipei,
10617 Taiwan
2Department of Energy and Refrigerating Airconditioning Engineering, Tung Nan University, 152
Beishen Road, Section 3, New Taipei City, 22202
Taiwan
3Department of Electrical Engineering, National Taiwan
University, 1, Roosevelt Road, Section 4, Taipei, 10617
Taiwan
4Epistar Corporation, Hsinchu, 30078 Taiwan
Optics Express
Vol. 22, Issue S3, pp. A842-A856 (2014)
The enhancement of output intensity, the
generation of polarized output, and the reduction
of the efficiency droop effect in a surface plasmon
(SP) coupled vertical light-emitting diode (LED)
with an Ag nano-grating structure located
between the p-GaN layer and the wafer bonding
metal for inducing SP coupling with the
InGaN/GaN
quantum
wells
(QWs)
are
demonstrated. In fabricating the vertical LED, the
patterned sapphire substrate is removed with a
photoelectrochemical liftoff technique. Based on
the reflection measurement from the metal
grating structure and the numerical simulation
result, it is found that the localized surface
plasmon (LSP) resonance induced around the
metal grating crest plays the major role in the SPQW coupling process although a hybrid mode of
LSP and surface plasmon polariton can be
generated in the coupling process. By adding a
surface grating structure to the SP-coupled
vertical LED on the n-GaN side, the output
intensity is further enhanced, the output
polarization ratio is further increased, and the
efficiency droop effect is further suppressed.
InGaN/GaN core-shell single nanowire light
emitting diodes with graphene-based p-contact
Maria Tchernycheva , Pierre Lavenus , Hezhi Zhang ,
Andrey V. Babichev , Gwenole Jacopin , Mehran
Shahmohammadi , François H. Julien , Rafal Ciechonski
, Giuliano Vescovi , and Olga Kryliouk
1 Institut d’Electronique Fondamentale, UMR 8622
CNRS, Université Paris Sud XI, 91405
Orsay cedex, France
2 St. Petersburg Academic University, Nanotechnology
Research and Education Centre,
Russian Academy of Science, Khlopina 8/3, 194021 St.
Petersburg, Russia
3 Ioffe Physical-Technical Institute of the Russian
Academy of Science, Polytechnicheskaya
26, 194021 St. Petersburg, Russia
4 ICMP LOEQ Ecole Polytechnique Fédérale de
Lausanne, 1015 Lausanne, Switzerland
5 GLO AB, Ideon Science Park, Scheelevägen 17, S-223
70 Lund, Sweden
6 GLO-USA, 1225 Bordeaux Dr, Sunnyvale, CA, 94086,
USA
Nano Letters
http://dx.doi.org/10.1021/nl5001295
We report on the demonstration of MOVPEgrown single nanowire InGaN/GaN core-shell light
emitting diodes (LEDs) with a transparent
graphene contact for hole injection. The electrical
homogeneity of the graphene-contacted LED has
been assessed by electron beam induced current
microscopy. By comparing graphene-contacted
and metal-contacted nanowire LEDs we show that
the
contact
layout
determines
the
electroluminescence
spectrum.
The
electroluminescence changes color from green to
blue with increasing injection current. Highresolution cathodoluminescence on cleaved
nanowires allows to locate with high precision the
origin of different emitted wavelengths and
demonstrates that the blue peak originates from
the emission of the radial quantum well on the mplanes, whereas the green peak arises from the
In-rich region at the junction between the mplanes and the semipolar planes. The spectral
behavior of the electroluminescence is
understood by modeling the current distribution
within the nanowire.
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Stress distribution in GaN nanopillars using
confocal Raman mapping technique
S. Nagarajan1,a), O. Svensk1, L. Lehtola1, H. Lipsanen1
and M. Sopanen1
1 Department of Micro and Nanosciences, Aalto
University, P.O. Box 13500, FI-00076 Aalto, Finland
Vol. 104, 151906 (2014)
http://dx.doi.org/10.1063/1.4872056
In this Letter, high-resolution confocal Raman
mapping of stress distribution in etched and regrown GaN nanopillar structures is investigated.
Results of the E2(high) phonon line mapping of
the top surfaces of individual nanopillars reveal
differences in stress between both the center and
edge of the nanopillar top surfaces and between
the etched and re-grown GaN nanopillar
structures. In-plane biaxial compressive stress
with the values of 0.36–0.42 GPa and 0.49–0.54
GPa is observed at the center of etched and regrown GaN nanopillars, respectively. The in-plane
biaxial compressive stress decreases from center
to edge in re-grown GaN nanopillar due to the
tilted facets. Also, the A1(LO) phonon frequency
increases from center to edges, or tilted facets,
due to the tilt of the c-axis of re-grown GaN
nanopillar.
NON/SEMI POLAR
Information selected by Philippe De Mierry
(CRHEA-CNRS)
Fabrication of m-axial InGaN nanocolumn arrays
on silicon substrates using triethylgallium
precursor chemical vapor deposition approach
Chia-Ming Liua, Yian Taia, Kuei-Hsien Chenb, Li-Chyong
Chenc
a Department of Chemical Engineering, National
Taiwan University of Science and Technology, Taipei
10617, Taiwan
b Institute of Atomic and Molecular Sciences, Academia
Sinica, Taipei 10617, Taiwan
c Center for Condensed Matter Sciences, National
Taiwan University, Taipei 10617, Taiwan
Volume 299, April 2014, Pages 92–96
We demonstrated the catalytic growth of m-axial
InxGa1−xN (0.10 ≤ x ≤ 0.17) nanocolumn arrays
with high crystallinity on silicon substrates using
metal–organic chemical vapor deposition with
trimethylindium (TMIn), triethylgallium (TEGa),
and ammonia as precursors. The high quality of
InGaN nanocolumns (NCs) were believed to be
due to the utilization of TEGa that achieved less
carbon impurities and offered more comparable
vapor pressure with that of TMIn at low
temperature. In addition, these NCs were grown
in non-polar m-axis, which the internal electric
field of the InGaN that often deteriorates the
device performances might be able to be
eliminated. Furthermore, the bandgap of this
InGaN can be modulated from UV to visible region
simply by tuning the ratio of the precursor during
the fabrication. Our results suggest an approach
to the fabrication of large-area NCs with a tunable
bandgap on a silicon substrate by the standard
MOCVD method that offers an immense
opportunity for electronic and photonic
applications and allows the scale-up from a
research laboratory to industrial scale.
Selective-area growth of GaN on non- and semipolar bulk GaN substrates
Shunsuke Okada1, Hideto Miyake1, Kazumasa
Hiramatsu1, Yuuki Enatsu2 and Satoru Nagao3
1 Department of Electrical and Electronic Engineering,
Mie University, Tsu 514-8507, Japan
2 Mitsubishi Chemical Corporation, Ushiku, Ibaraki 3001295, Japan
3 Mitsubishi Chemical Group Science and Technology
Research Center, Inc., Yokohama 227-8502, Japan
Japanese Journal of Applied Physics
Vol. 53; 05FL04
http://dx.doi.org/10.7567/JJAP.53.05FL04
We carried out the selective-area growth of GaN
and fabricated InGaN/GaN MQWs on non- and
semi-polar bulk GaN substrates by MOVPE. The
differences in the GaN structures and the In
incorporation of InGaN/GaN MQWs grown on
non- and semi-polar GaN substrates were
investigated. In the case of selective-area growth,
different GaN structures were obtained on
$(20\bar{2}1)$ GaN, $(20\bar{2}\bar{1})$ GaN,
and $(10\bar{1}0)$ GaN substrates. A repeating
pattern of $\{ 1\bar{1}01\} $ and $\{
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1\bar{1}0\bar{1}\} $ facets appeared on
$(20\bar{2}1)$ GaN. Then, we fabricated
InGaN/GaN MQWs on the facet structures on
$(20\bar{2}1)$ GaN. The emission properties
characterized by cathodoluminescence were
different for $\{ 1\bar{1}01\} $ and $\{
1\bar{1}0\bar{1}\} $ facets. On the other hand, for
InGaN/GaN MQWs on non- and semi-polar GaN
substrates, steps along the a-axis were observed
by AFM. In particular on $(20\bar{2}1)$ GaN,
undulations and undulation bunching appeared.
Photoluminescence characterization indicated
that In incorporation increased with the off-angle
from the m-plane and also depended on the
polarity
Polarized XAFS study of Al K-edge for m-plane
AlGaN films
T Miyanaga1, T Azuhata1, K Nakajima1, H Nagoya1, K
Hazu2 and S F Chichibu2
1 Department of Advanced Physics, Hirosaki University,
Hirosaki, Aomori 036-8561, Japan
2 Institute of Multidisciplinary Research for Advanced
Materials and Department of Applied Physics, Tohoku
University, Aoba, Sendai 980-8577, Japan
Journal of Physics: Conference Series
Vol. 502; 012031
http://dx.doi.org/10.1088/1742-6596/502/1/012031
Local structures around Al atoms in high-quality
m-plane AlxGa1-xN films (x=0.32 and 0.58)
deposited on m-plane GaN substrates by the NH3
source molecular beam epitaxy method were
investigated by Al K-edge X-ray absorption fine
structure (XAFS) for the first time. XAFS spectra
were measured using a linearly-polarized X-ray
source from synchrotron radiation for three
different directions; along the c-, a-, and m-axes.
The interatomic distances along the a-axis are
close to Ga-Ga distance in GaN, indicating that the
local structures are strongly affected by GaN
substrates. The localization of Al atoms was
observed for the Al0.32Ga0.68N film.
Comparative study of field-dependent carrier
dynamics and emission kinetics of InGaN/GaN
light-emitting diodes grown on (112¯2) semipolar
versus (0001) polar planes
Yun Ji1, Wei Liu1, Talha Erdem2, Rui Chen1, Swee Tiam
Tan1, Zi-Hui Zhang1, Zhengang Ju1, Xueliang Zhang1,
Handong Sun1, Xiao Wei Sun1, Yuji Zhao3, Steven P.
DenBaars3,a), Shuji Nakamura3 and Hilmi Volkan
Demir1,2,a)
1 LUMINOUS! Centre of Excellence for Semiconductor
Lighting and Displays, School of Electrical and
Electronic Engineering, School of Physical and
Mathematical Sciences, Nanyang Technological
University, 50 Nanyang Avenue, Singapore 639798
2 Department of Electrical and Electronics, Department
of Physics, and UNAM–Institute of Material Science
and Nanotechnology, Bilkent University, Ankara TR06800, Turkey
3 Electrical and Computer Engineering and Materials
Department, University of California, Santa Barbara,
California 93106, USA
Vol. 104, 143506 (2014);
http://dx.doi.org/10.1063/1.4870840
The characteristics of electroluminescence (EL)
and photoluminescence (PL) emission from GaN
light-emitting diodes (LEDs) grown on (11 2¯ 2)
semipolar plane and (0001) polar plane have been
comparatively investigated. Through different
bias-dependent shifting trends observed from the
PL and time-resolved PL spectra (TRPL) for the two
types of LEDs, the carrier dynamics within the
multiple quantum wells (MQWs) region is
systematically analyzed and the distinct fielddependent emission kinetics are revealed.
Moreover, the polarization induced internal
electric field has been deduced for each of the
LEDs. The relatively stable emission behavior
observed in the semipolar LED is attributed to the
smaller polarization induced internal electric field.
The study provides meaningful insight for the
design of quantum well (QW) structures with high
radiative recombination rates.
The effects of substrate nitridation on the
growth of nonpolar a-plane GaN on r-plane
sapphire by metalorganic chemical vapor
deposition
Jun Zhanga, Wu Tiana, Feng Wua, Qixin Wana, Zhujuan
Wanga, Jin Zhanga, Yulian Lia, Jiangnan Daia, Yanyan
Fanga, Zhihao Wua, Changqing Chena, Jintong Xub,
Xiangyang Lib
a Wuhan National Laboratory for Optoelectronics,
Huazhong University of Science and Technology,
Wuhan 430074, People's Republic of China
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b Key Laboratory of Infrared Imaging Materials and
Detectors, Shanghai Institute of Technical Physics,
Chinese Academy of Sciences, Shanghai 200083,
People's Republic of China
The effects of substrate nitridation on the growth
of nonpolar a-plane GaN directly deposited on rplane sapphire by metalorganic chemical vapor
deposition (MOCVD) were investigated. Using
nitridation, high-quality a-plane GaN with flat
surface was acquired. On the contrary, if the
nitridation layer was removed, the epitaxial aplane GaN exhibited deep triangular pits and poor
crystalline properties. This could be attributed to
the fact that uniform-distributed AlN grains were
introduced by nitridation, which might act as the
nucleation layer for the following a-plane GaN
growth. The effects of substrate nitridation on the
evolutions of anisotropic morphologies and
crystalline properties were also studied by
artificially interrupting the growth at different
stages. The consequences suggested the
nitridation layer could contribute to surface
coalescence of a-plane GaN. The reasons
responsible for this phenomenon were probed by
Raman spectrum, and a model was proposed to
explicate the effects of nitridation on the growth
of a-plane GaN.
Stacking faults and interface roughening in
semipolar (202¯1¯) single InGaN quantum wells
for long wavelength emission
Feng Wu1, Yuji Zhao1, Alexey Romanov1,2,3,4, Steven
P. DenBaars1, Shuji Nakamura1 and James S. Speck1
1 Materials Department, University of California, Santa
Barbara, California 93106, USA
2 Ioffe Physical-Technical Institute, Russian Academy of
Science, St. Petersburg 194021, Russia
3 ITMO University, St. Petersburg 197101, Russia
4 Institute of Physics, University of Tartu, Tartu 51014,
Estonia
Vol. 104, 151901 (2014);
http://dx.doi.org/10.1063/1.4871512
The microstructure of InGaN single quantum wells
(QWs) grown in semipolar (202¯1¯) orientation on
GaN substrates was studied by transmission
electron microscopy. Stress relaxation in the
lattice mismatch InxGa1−xN layer was realized by
forming partial misfit dislocations associated with
basal plane stacking faults (BPSFs). For given
composition x = 0.24, BPSFs formation was
observed when the QW thickness exceeded 4 nm.
The high density of partial threading dislocations
that bound the BPSFs is detrimental to lightemitting
device
performance.
Interface
roughening (faceting) was observed for both
upper and lower QW interfaces (more
pronounced for upper interface) and was found to
increase with the thickness of the QW. BPSFs had
a tendency to nucleate at roughened interface
valleys.
OTHER
Information selected by Agnès Trassoudaine
(Univ D’Auvergne)
The control of mechanical bow for GaN substrate
grown by HVPE with relatively longer radius of
lattice curvature
Hae-Yong Lee1,*, Young-Jun Choi1, Jin-Hun Kim1,
Hyun-Soo Jang1, Hae-Kon Oh1, Jun Young Kim1, Jung
Young Jung1 andJonghee Hwang2
1LumiGNtech Co., Ltd., Room 206, Business Incubator
Bldg., 233-5 Gasan-Dong, Guemcheon-Gu, 153-801
Seoul, Korea
2Korea Institute of Ceramic Engineering and
Technology (KICET), 233-5 Gasan-Dong, GuemcheonGu, 153-801 Seoul, Korea
We are going to develop GaN growth process by
HVPE method, which shows the near null value of
free standing (FS)-GaN wafer bowing after laser
lift-off (LLO) process in order to reduce the
production cost of GaN substrate. The 309 to 318
µm thick HVPE grown GaN layers on sapphire
shows 574 to 669 µm of as grown bows, and –299
to 95 µm of bow after LLO process. The 440 µm
thick HVPE grown GaN layer on sapphire shows
693 µm of as grown bow, and –4 µm of bow after
LLO process. From this GaN template, we could
get the 356 µm thick FS-GaN wafer with 2 µm of
bow after polishing. This GaN substrate shows at
least 43.87 m of the radius of lattice curvature
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evaluated by 9-points measuring of (004) rocking
curve along center line parallel to the main flat
plane.
Effect of annealing temperature on IR-detectors
based on InN nanostructures
M. Amirhoseiny, Z. Hassan, S.S. Ng, G. Alahyarizadeh
Nano-Optoelectronics Research and Technology
Laboratory, School of Physics, Universiti Sains Malaysia,
11800 Penang, Malaysia
Vacuum
Volume 106, August 2014, Pages 46–48
http://dx.doi.org/10.1016/j.vacuum.2014.03.010
We report the fabrication of InN nanostructure
sensitive photodetector grown expitaxially on a
silicon (110) substrate by RF sputtering at room
temperature. X-ray diffraction measurement
shows that the deposited InN film has (101)
preferred growth orientation and wurtzite
structure. The platinum (Pt) Schottky contact was
deposited via thermal vacuum evaporation (10−5
Torr) by using a metal semiconductor metal
(MSM) mask. Measurements utilizing the IR
source indicate that the barrier height as well as
the ideality factor are temperature dependent.
The use of (110) orientation of silicon has the
potential of increasing the detector quality with
electronics intrinsically higher electron mobility.
Such systems are interesting for optoelectronic
applications in the IR region.
In-situ decomposition and etching of AlN and
GaN in the presence of HCl
Dirk Fahlea, Thomas Krueckenb, Martin Dauelsbergb,
Holger Kalischa, Michael Heukena, b, Andrei Vescana
a GaN Device Technology, RWTH Aachen University,
Sommerfeldstr. 24, 52074 Aachen, Germany
b AIXTRON SE, Kaiserstr. 98, 52134 Herzogenrath,
Germany
Volume 393, 1 May 2014, Pages 89-92
We propose a two-step reaction in which the first
step, the decomposition of GaN, is the limiting
one. The second step consists of a reaction of Ga
with HCl to form volatile GaCl. We noticed that
the decomposition step is enhanced with
increased hydrogen partial pressure. Further, we
observed that a coverage of the surface with Ga
enhances the decomposition rate. By using a
pulsed supply of HCl into the reactor a Ga-rich
surface was maintained and the etch rate
enhanced up to a temperature of 830 °C.
Structural and optical
AlGaN/GaN layers
characterization
of
M. Jayasakthi, R. Ramesh, P. Arivazhagan, R.
Loganathan, K. Prabakaran, M. Balaji, K. Baskar
Crystal Growth Centre, Anna University, Chennai–600
025, India
High quality AlxGa1−xN layers have been grown
on c-plane sapphire substrate by Metal Organic
Vapor Phase Epitaxy. The aluminum (Al)
composition was varied from 15% to 51%. When
the flow rate of trimethylaluminum increased, the
growth rate was found to be decreased. The
crystalline quality of AlGaN layers has been
evaluated using High Resolution X-ray Diffraction
rocking curves. Reciprocal Space Mapping results
confirmed that in low Al composition (x=0.15),
AlGaN layers are found to be fully strained. In high
Al composition (x=0.33, 0.51), the AlGaN layers
are relaxed by generations of cracks due to lattice
mismatch. The optical properties of AlGaN/GaN
layers have been investigated by room
temperature
Photoluminescence.
While
increasing the Al content, the AlGaN emission
peak has been found to shift towards higher
energies. The surface morphology and roughness
of AlGaN has been studied by Atomic Force
Microscopy. Root Mean Square roughness values
have been found to increase with the increase of
Al.
The etch rates of gaseous HCl on AlN and GaN in
H2 ambient in a MOVPE reactor have been
studied. For AlN, etching by HCl in H2 and N2 is
compared. When etching GaN in hydrogen by HCl,
a dependency of etch rate on temperature was
found and the activation energy was determined.
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Morphology, growth mode and indium
incorporation of MOVPE grown InGaN and
AlInGaN: A comparison
J.-P. Ahla, b, J. Hertkorna, H. Kocha, B. Gallera, B.
Michela, M. Bindera, B. Holländerc
a OSRAM Opto Semiconductors GmbH, 93055
Regensburg, Germany
b Institute of Optoelectronics, University of Ulm, 89069
Ulm, Germany
c PGI-9, Forschungszentrum Jülich GmbH, 52425 Jülich,
Germany
We compared InGaN- and AlInGaN-layers grown
by metal-organic vapor phase epitaxy (MOVPE) in
terms of morphology, growth mode and indium
incorporation. The growth parameters of the
AlInGaN layers only differed from InGaN growth
by an additional trimethylaluminum (TMAl) flow.
Rutherford backscattering spectrometry (RBS) and
X-ray
photoelectron
spectroscopy
(XPS)
measurements showed that the indium
incorporation in AlInGaN was significantly
increased compared to InGaN. Atomic force
microscopy (AFM) was used to analyze the
morphology and growth mode. The additional
TMAl flow changed the growth mode from a stepflow mode to a 2-dimensional (2D) island
nucleation mode, yielding a smoother layer
morphology. This behavior can be explained by
the low surface mobility of the Al adatoms and
their nucleation on terraces between adjacent
steps. Step bunching - as observed for InGaN - was
avoided during AlInGaN growth. This reduced the
AFM root mean square roughness by 40%
compared to InGaN. Possible impacts on charge
carrier localization in QWs are discussed.
Preparation of free-standing GaN substrates
from GaN layers crystallized by hydride vapor
phase epitaxy on ammonothermal GaN seeds
Tomasz Sochacki1,2, Mikolaj Amilusik1,2, Boleslaw
Lucznik1,2, Michal Fijalkowski1, Janusz Ludwik
Weyher1, Bohdan Sadovyi1, Grzegorz Kamler1,
Grzegorz Nowak1, Elzbieta Litwin-Staszewska1,
Aleksander Khachapuridze1, Izabella Grzegory1, Robert
Kucharski3, Marcin Zajac3, Roman Doradzinski3 and
Michal Bockowski1,2
Japanese Journal of Applied Physics
Vol.53; 05FA04
http://dx.doi.org/10.7567/JJAP.53.05FA04
Crystallization of GaN by hydride vapor phase
epitaxy (HVPE) on ammonothermally grown GaN
seed crystals is overviewed. Morphology of the
crystal growing surface at the beginning of the
crystallization process and at the end of it is
presented. Based on these results a rough growth
model is proposed. Smooth GaN layers up to 1
mm thick and of a high purity, excellent crystalline
quality, without any cracks, and with a low
dislocation density are grown. Preparation of the
free-standing HVPE-GaN crystals by slicing as well
as structural, electrical and optical qualities of the
resulting wafers are reported and discussed.
Self-annihilation of inversion domains by high
energy defects in III-Nitrides
T. Koukoula1, J. Kioseoglou1,a), Th. Kehagias1, A. O.
Ajagunna2, Ph. Komninou1 and A. Georgakilas2
"1 Department of Physics, Aristotle University of
Thessaloniki, GR-54124 Thessaloniki, Greece
2 Microelectronics Research Group, IESL, FORTH, P.O.
Box 1385, GR-71110 Heraklion, Crete, Greece and
Department of Physics, University of Crete, P.O. Box
2208, GR-71003 Heraklion, Crete, Greece"
Vol. 104, 141914 (2014);
http://dx.doi.org/10.1063/1.4871302
Low-defect density InN films were grown on
Si(111) by molecular beam epitaxy over an ∼1 μm
thick GaN/AlN buffer/nucleation layer. Electron
microscopy observations revealed the presence of
inverse polarity domains propagating across the
GaN layer and terminating at the sharp GaN/InN (
0001¯ ) interface, whereas no inversion domains
were detected in InN. The systematic annihilation
of GaN inversion domains at the GaN/InN
interface is explained in terms of indium
incorporation on the Ga-terminated inversion
domains forming a metal bonded In-Ga bilayer, a
structural instability known as the basal inversion
domain boundary, during the initial stages of InN
growth on GaN.
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Influence of 3C-SiC/Si(1 1 1) template properties
on the strain relaxation in thick GaN films
Y. Cordiera, E. Frayssineta, M. Portaila, M. Zielinskib, T.
Chassagneb, M. Korytova, A. Courvillea, S. Roya, M.
Nemoza, M. Chmielowskaa, P. Vennéguèsa, H.P.D.
Schenkc, M. Kennardc, A. Bavardd, 1, D. Rondid, 1
a CRHEA-CNRS, Rue Bernard Grégory, Sophia Antipolis,
06560 Valbonne, France
b NOVASiC, Savoie Technolac, Arche Bât. 4, BP 267,
73375 Le Bourget du Lac Cedex, France
c SOITEC Specialty Electronics, Place Marcel Rebuffat,
Z.A. Courtabœuf 7, 91140 Villejust, France
d OMMIC, 2 chemin du Moulin, B.P. 11, 94453 LimeilBrévannes Cedex, France
In this work, we study the influence of 3C-SiC/Si(1
1 1) template parameters (thickness, roughness
and substrate miscut) on the GaN crystal quality
and its strain state. For this, structures with an
AlN nucleation layer and 1 to 4 µm thick GaN layer
have been grown by molecular beam epitaxy in
order to select the best templates for the growth
of thick GaN structures. Similar GaN structures
have been grown directly on silicon for
comparisons. The influence of the high silicon
doping is confirmed on the enhancement of strain
relaxation. Despite this limitation, a 5 µm thick
crack-free continuous GaN structure (with 1 µm
silicon doped) has been successfully grown on the
best selected template. Furthermore, the growth
by metal organic chemical vapor deposition of
structures with AlN and SiN inter-layers and thick
continuous GaN layers on Si(1 1 1), 3C-SiC/Si(1 1
1) and SoPSiC (silicon on polycrystalline silicon
carbide) has been achieved in order to show the
relative benefit of each approach in terms of layer
quality and strain state.
Effect of c-plane sapphire substrate miscut angle
on indium content of MOVPE-grown N-polar
InGaN
Kanako Shojiki1, Jung-Hun Choi1,2, Hirofumi Shindo1,
Takeshi Kimura1,2, Tomoyuki Tanikawa1,2, Takashi
Hanada1,2, Ryuji Katayama1,2 and Takashi
Matsuoka1,2
1 Institute for Materials Research, Tohoku University,
Sendai 980-8577, Japan
2 CREST, Japan Science and Technology Agency,
Kawaguchi, Saitama 332-0012, Japan
apanese Journal of Applied Physics
Vol. 53 05FL07
http://dx.doi.org/10.7567/JJAP.53.05FL07
Nitrogen-polar (N-polar) InGaN films were grown
on a GaN template/c-plane sapphire substrate by
metal–organic vapor phase epitaxy (MOVPE). The
effects of c-plane sapphire substrate miscut angle
on the indium (In) content and crystal properties
of N-polar InGaN films were investigated. The In
content increased with increasing miscut angle in
the vicinal region of less than 1.1°. This tendency
is different from that of group-III-polar InGaN
growth because of the difference in the atomic
arrangement on the terraces and at step edges
between these two inverted polar surfaces. In the
case of N-polar growth, a spontaneous twodimensional nucleation on terraces is difficult and
the intentional introduction of steps is effective
compared
with
group-III-polar
growth.
Furthermore, by observing the surface
morphologies of GaN templates in view of both
macroscopic and microscopic scales, a clear
relationship between the macroscopic surface
structure of GaN template and the In content of
InGaN was revealed.
Fabrication of free-standing GaN by using
thermal decomposition of GaN
Sinae Kima, Hyunjae Leeb, Siyoung Kimb, Sungkuk
Choia, Jieun Kooa, Jiho Changa
a Department of Nano-semiconductor, Korea Maritime
and Ocean University, Busan 606-791, Korea
b PAN-crystal, Suwon 443-380, Korea
Free-standing GaN wafers were fabricated by
hydride vapor phase epitaxy (HVPE) using an insitu self-separation technique. Separation of GaN
happened during the high-temperature GaN
growth through thermal decomposition of the
decomposable buffer layer (DBL). We optimized
the growth condition of DBL, which affects not
only the separation property but also the
crystallinity of GaN. Free standing GaN revealed
negligible residual stress, narrow (0002) omega
rocking curve linewidth (67 arcsec), and low etch
pit density (6×106 cm−2) as well. The carrier
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concentration of 4×1018 cm−3 and mobility of
150 cm2/Vs was observed from Hall effect
measurement. Those results showed the
feasibility of in-situ self-separation method to
obtain high quality free-standing GaN wafer.
Epitaxial lateral overgrowth of nitrogen-polar
(000-1) GaN by metalorganic chemical vapor
deposition
Jie Song , Ge Yuan , Kanglin Xiong , Benjamin Leung ,
and Jung Han
Department of Electrical Engineering, Yale University,
New Haven, CT 06511, USA
Crystal Growth & Design
http://dx.doi.org/10.1021/cg500229r
Epitaxial lateral overgrowth (ELO) of nitrogenpolar (000-1) GaN (N-polar GaN) by metalorganic
vapor deposition has been studied. The influence
of growth conditions on the lateral growth is
investigated and a correlation of growth
conditions with the observed inversion of polarity
is established. Most of the observed trends for Npolar ELO are contrary to those reported from Gapolar experiments. Such differences are explained
by considering the property of surface reactivity
of N-polar GaN with hydrogen species. Based on
the trends of the occurrence (or absence) of
polarity inversion, an atomistic model is proposed
to explain the origin of polarity inversion. This
model also enables us to control the process and
to completely eliminate polarity inversion,
resulting in fully-coalesced, purely N-polar GaN
with an improved crystalline quality.
Comprehensive analysis of the surface and crystal
properties has been performed at clean c -plane
sapphire substrates, sapphire layers after
nitridation, and subsequently grown InN layers
deposited by metal–organic vapor phase epitaxy.
The (1×1) surface of clean sapphire reconstructs
into a (View the MathML source×View the
MathML source)R±9° structure after annealing at
1050 °C, which was performed prior to the
nitridation process. The formation of crystalline
AlN was observed for nitridation above 800 °C. Xray photoelectron spectroscopy performed on the
nitridated layers shows that N-Al chemical bonds
dominate this structure, while the number of N-O
bonds is negligibly small. Amorphous AlNxOy
layers form during nitridation below 800 °C,
where N-O bonds dominate. All layers formed by
nitridation show defects associated with N bonds.
The morphology of the nitridated layers affects
the surface and crystal quality of the subsequently
grown polar InN layers. N-polar InN layers with a
smooth surface and single crystalline structure
were grown on the AlN nitridated layers, while Inpolar InN layers with a rough surface and a
polycrystalline structure were grown on the
amorphous nitridated layers.
Surface and crystal structure of nitridated
sapphire substrates and their effect on polar InN
layers
D. Skuridinaa, D.V. Dinha, 1, M. Pristovseka, 2, B.
Lacroixb, 3, M.-P. Chauvatb, P. Ruteranab, M. Kneissla,
P. Vogta
a Institut für Festkörperphysik, Technische Universität
Berlin, Hardenbergstraße 36, 10623 Berlin, Germany
b CIMAP, UMR 6252, CNRS-ENSICAEN-CEA-UCBN, 6, Bd
MarView the MathML sourcechal Juin, 14050 Caen
Cedex 4, France
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PRESS RELEASE
Technical and economic information selected by Knowmade
OPTOELECTRONICS
Martini Tech offering GaN MOCVD on sapphire
substrates
Semiconductor Today
Martini Tech Inc of Tokyo, Japan has started to
offer a new gallium nitride (GaN) metal-organic
chemical vapour deposition (MOCVD) service on
sapphire substrates for LED applications.
Founded in 2013, Martini Tech offers
microfabrication services including micro-electromechanical system (MEMS) design, development
and foundry, sapphire wafer patterning,
nanoimprint mold manufacturing (using materials
such as silicon, nickel and quartz), nanoimprint
replica on film, GaN on patterned sapphire
substrates (PSS) deposition by MOCVD, and
sputtering deposition services (with more than
120 different materials available).
Widespread adoption of LEDs has so far been
hindered by factors including relatively high price
and lower light output compared with traditional
incandescent light bulbs, notes Martini Tech. One
of the most promising techniques for improving
the light output of LEDs involves the deposition of
a thin GaN epitaxial layer on a patterned sapphire
substrate (PSS), adds the firm.
The service offered by Martini Tech includes
MOCVD of undoped GaN and of n- or p-doped
GaN for high-quality highly ordered crystalline
layers up to 5µm thick.
Read more
Toshiba launches 1W and 0.6W white LEDs for
lighting applications
Semiconductor Today
Tokyo-based
semiconductor
manufacturer
Toshiba Corp has launched two new series of
white LEDs: the 3.5mm x 3.5mm lens package 1W
type TL1L2 series and the 3.0mm x 3.0mm flat
package 0.6W type TL3GB series.
Utilizing gallium nitride-on-silicon (GaN-on-Si)
process technology developed for LED lighting, the
new white LEDs realize a low forward voltage (VF)
and low power consumption and can contribute to
cost reductions, the firm says.
For the TL1L2 series, VF is 2.85V at a forward
current (IF) of 350mA. Luminous efficacy is
135lm/W (5000K, Ra70) at 1W operation
(IF=350mA). Applications include sources for
general lighting (including light bulbs, base lights,
down lights and ceiling lights), street lights and
floodlights.
For the TL3GB series, VF is 5.76V at an IF of
100mA. Luminous efficacy is 118lm/W (5000K,
Ra80) at 0.6W operation (IF=100mA). Applications
include sources for general lighting (including light
bulbs, base lights, down lights and ceiling lights).
For both series, six color temperatures are
available, from 2700K to 6500K. Mass production
will start at the end of March.
Read more
Toshiba launches CSP white LEDs for lighting,
cutting mounting area by 90%
Semiconductor Today
Tokyo-based
semiconductor
manufacturer
Toshiba Corp has launched ultra-small chip-scalepackage (CSP) white LEDs for lighting applications
that can reduce the mounting area by 90%
compared to conventional 3.0mm x 1.4mm
packaged products, the firm reckons.
Toshiba’s chip-scale-package white LEDsPicture:
Toshiba’s chip-scale-package white LEDs.
The new products use gallium nitride-on-silicon
(GaN-on-Si) and a new process technology that
fabricates the elements of a packaged LED on an
8-inch silicon wafer. With a package size of just
0.65mm x 0.65mm, the LEDs are reckoned to be
the industry’s smallest in the sub-watt class (1/41/2W) of white LEDs. However, they achieve
luminous efficacy of 130lm/W (during 60mA
operation) and what is claimed to be superior heat
dissipation. Maximum forward current is 180mA.
The color temperature is 5000K and the color
rendering index (Ra) is 80 (minimum). Other
planned color variants include 4000K, 3000K and
2700K.
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Using the new white LEDs makes it possible to
achieve a narrow beam in small-size lighting
equipment, says Toshiba. Applications of the
TL1WK series LEDs are light sources for general
lighting, including straight tube lights, light bulbs
and ceiling lights.
The TL1WK series LEDs are being showcased at
the Light+Building 2104 trade fair in Frankfurt,
Germany (30 March to 4 April). Sample shipments
will start in April.
Read more
Samsung launches flip-chip LED packages and
modules for size-sensitive lighting applications
Semiconductor Today
Picture: Samsung’s flip-chip on module solution.
South Korea’s Samsung Electronics Co Ltd has
introduced a new lineup of flip-chip LED packages
and modules offering enhanced design flexibility
and a high degree of reliability, for use in LED
lighting such as LED bulbs, MR/PAR and
downlights.
“By utilizing an advanced flip-chip technology,
Samsung has made significant improvements to its
LED packages and modules,” says Bangwon Oh,
senior VP, LED strategic marketing team. “Our
new Samsung FC and FCOM solutions also
strengthen our overall line-up of LED component
solutions.”
Samsung’s new flip-chip (FC) LED package and flipchip on module (FCOM) solutions feature what are
claimed to be highly efficient and versatile LED
structures, created by flipping over blue LED chips
and adhering phosphor film to each of them.
Unlike conventional LED packages that dispense
phosphor and then place a plastic mold over each
chip, Samsung’s FC package technology can
produce LED packages down to a chip-scale size
without any mold, enabling more compact lighting
fixture designs.
Samsung’s new FC and FCOM series can be driven
at a current higher than that of conventional LED
components, and have low thermal resistance.
The low thermal resistance improves the reliability
of the FC and FCOM solutions, resulting in higher
flux and a decrease in the number of packages
needed, plus a reduction in the size of the circuit
board, reckons Samsung.
Also, by attaching a cell film, each package gains
uniform thickness and lower color deviation. The
FC and FCOM solutions hence provide a high level
of color consistency and ensure the chromaticity
control of MacAdam 3-step ellipses.
The new FC and FCOM LED solutions include a
mid-power LED package (LM131A), a high-power
LED package (LH141A) and an LED downlight
module, all featuring the new flip chip technology.
Flip-chip mid-power and high-power LED packages
The LM131A and LH141A flip-chip packages
feature compact form factors of 1.22mm x
1.22mm and 1.4mm x 1.4mm, respectively. By
excluding a plastic mold, the two packages can
function at a high current level in a highly reliable
manner, even after long hour of use, says
Samsung. These advantages make them suitable
for use in LED lighting applications requiring a
small form factor with high light output, including
LED bulbs and spotlight products such as MRs and
PARs. In addition, the use of a phosphor film
assures color quality that satisfies the MacAdam
3-step, adds the firm.
FCOM for LED downlight fixtures
Compared to a chip-on-board (COB) engine, which
has a fixed wattage, the new FCOM permits
simple adjustments in the number of FC LED
packages to make the module compatible with a
variety of electrical drivers of different wattages,
allowing greater design flexibility, says Samsung.
Samsung’s flip-chip on module solutionPicture:
Samsung’s flip-chip on module solution.
To create a downlight with 1000lm output and
100lm/W luminous efficacy, the FCOMs require a
1.7cm x 1.7cm circuit. Such a small form factor
suits size-sensitive LED lighting applications,
including LED bulbs, MR/PAR spotlights,
downlights and even cove lighting, the firm adds.
The FCOMs satisfy the MacAdam 3-step and can
support MacAdam 2-step (depending on user
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35
needs) due to the color consistency of the chips
and a color rendering index (CRI) of at least 80.
The new FCOMs also offer a range of correlated
color temperatures (CCT), from 2700K to 5000K.
The new LED solutions are being showcased in
booth B04, Hall 6.2, at the Light and Building 2014
trade fair in Frankfurt, Germany (30 March – 4
April). The products will be available on the
market in second-quarter 2014.
Read more
A $10 Revolution?
Compound Semiconductor
Flat as a pancake: Using mid-power Luxeon LEDs,
SlimStyle uses 10.5W of power to put out some 800
lumens.
Does the release of the $9.97 Philips' SlimStyle
LED bulb represent a tipping point for the uptake
of solid-state lighting? Compound Semiconductor
investigates.
Earlier this year, Philips unveiled the world's first
flat light bulb, called 'SlimStyle'. In an unusual
move, designers have flattened the bulb to boost
its surface area so individual LEDs can be
sufficiently spaced out to remain cool. Crucially,
this removes the need for the heatsink found at
the base of most bulbs.
The 60W-equivalent soft white lamp boasts similar
credentials to Cree's rival bulb, producing 800
lumens using 10.5W, offering 76.2 lumens per
Watt with 25,000 hours of life. Admittedly, the
'SlimStyle' bulb doesn't provide the dazzling 93.8
lumens per Watt of its L Prize winning
predecessor, but at $9.97, consumers can bask in
an efficient and affordable glow.
Right now, Philips is waiting on Energy Star
certification; Cree has pipped the Dutch
technology giant to the post here. But with each
hitting the all-important $10 price point, Philips'
SlimStyle 60W equivalent soft white bulb is Cree's
only real competition, for the time being.
Read more
Soraa unveils LED AR111, PAR30 and PAR38
lamps
Semiconductor Today
Soraa Inc of Fremont, CA, USA, which develops
solid-state lighting technology built on ‘GaN on
GaN’ (gallium nitride on gallium nitride)
substrates, has launched a full range of LED
AR111, PAR30 and PAR38 lamps that will be
available to ship in late second-quarter 2014.
All Soraa lamps feature three-phosphor LEDs with
a violet pump that enable benefits such as pointsource optics for uniform beams of high-intensity
Violet 3-Phosphor (VP3) Natural White and VP3
Full-spectrum Vivid Color. Now, Soraa’s LED lamps
are available in a portfolio of larger form factors
essential for retail, hospitality and residential
applications.
Soraa’s large lamp portfolio of AR111, PAR30 Long
Neck (LN), PAR30 Short Neck (SN) and PAR38
lamps achieve 1000 lumen output with VP3
Natural White and VP3 Vivid Color technology,
defined by full-visible-spectrum, high-whiteness
rendering, 95-CRI, and 95-R9. The family of large
lamps will be available in 25°, 36° and 60° beam
angles, and in a wide range of color temperatures.
The AR111 is an important lamp for object
lighting, requiring narrow spots, crisp beam edges,
and no glare. With a peak intensity of 27,500Cd,
Soraa’s 8°95-CRI/95-R9 AR111 is claimed to be the
only LED product that matches halogen levels
(50% higher than the nearest 80-CRI competitor).
The PAR30LN and PAR30SN lamps offer what is
claimed to be the only 8° narrow-spot option on
the market without active cooling, achieving a
center-beam intensity of 28,250Cd (more than
twice the level of the nearest 80-CRI competitor)."
Read more
KnowMade
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The 300 lm/W barrier broken by Cree
LEDs in signage & professional displays to grow
at 11.9% annually to $3.56bn in 2019
i-micronews
Semiconductor Today
Cree, Inc. (Nasdaq: CREE) records another
significant LED milestone with the demonstration
of 303 lumens per watt from a white, high-power
LED.
Reaching the landmark achievement much faster
than previously believed possible, this result
surpasses Cree’s previous R&D industry-best of
276 lumens per watt announced just over a year
ago.
Cree Reaches 303-LPW LED Milestone“This is truly
an impressive accomplishment. Achieving this
level of LED efficacy amplifies the potential for the
solid-state-lighting industry to deliver smaller,
lower-cost lighting solutions, and even largerthan-expected energy savings,” said Steven
DenBaars, professor and co-director, Solid State
Lighting and Energy Center, University of
California, Santa Barbara.
Cree reports that the LED efficacy was measured
at 303 lumens per watt, at a correlated color
temperature of 5150 K and 350 mA. Standard
room temperature was used to achieve the
results.
“Relentless innovation is a driving force at Cree as
we continue the pursuit of 100-percent LED
adoption,” said John Edmond, Cree co-founder
and director of advanced optoelectronics.
“Pushing the boundaries of LED performance is
critical to enhancing LED lighting designs, and this
303 lumens-per-watt result will enable more costeffective lighting solutions.”
Read more
Global consumption of packaged LED chips used in
signage/professional displays will rise at an
average annual rate of 11.9% from nearly $2bn in
2014 to $3.56bn in 2019, forecasts a new study
from market research firm ElectroniCast
Consultants.
Demand is climbing for applications including
indoor and outdoor signage/displays used in
airports, shopping centers, roadways, sport
venues, hospitals, hotels, business centers, and
public transit vehicles and stations, says
ElectroniCast.
“In 2014, the use of LEDs in lighting, especially in
signage and display applications, is fully set in the
growth stage in the product life cycle (PLC),
especially in digital signage and TV-type
(commercial TV) displays and large-format
displays (LFDs) sold through the B2B (business-tobusiness) activity,” says Stephen Montgomery,
director of ElectroniCast’s LED Lighting market
research group.
“This application covers LEDs used in stationary
and vehicle-based signs and displays,” he adds.
“LEDs are used in building facades, airports and
public transit stations, large outdoor video
screens, digital billboards, sport/stadium displays,
small indoor retail displays, food displays
(restaurants/supermarkets), signs on taxis and
destination signs on mass-transit vehicles,
channel-lettering/light-boxes, LED/LCD TV screens
(used exclusively for professional display
purposes), and the list continues.”
The market forecast covers standard-type versus
high-brightness (HB)-type LEDs used in signage
and professional displays. In terms of value, HBLEDs are forecast to maintain the market share
lead. However, in terms of volume (the number of
LEDs), standard-type LEDs dominate in market
share, since there is a huge difference in average
selling prices (ASPs) between HB-LEDs and
standard LEDs, notes ElectroniCast.
Read more
KnowMade
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Trifortune orders Aixtron MOCVD system for GaN
LEDs on alternative substrates
Semiconductor Today
Deposition equipment maker Aixtron SE of
Aachen, Germany says that Jiangsu Trifortune
Electronic Technology Co Ltd of Jintan City, China
has ordered an AIX G5 HT metal-organic chemical
vapor deposition (MOCVD) system to develop
gallium nitride (GaN)-based high-brightness lightemitting diodes (HB-LEDs).
Trifortune was founded in May 2013. In phase one
of its strategic business plan the firm made an
initial investment into a pre-production
demonstration line located at Shahe, Beijing.
The new system will be equipped to handle 56x2inch wafers per run and will be installed at
Trifortune’s R&D center. The developed process
will be transferred to mass production in the
Jiangsu area upon completion of the research.
“We are developing GaN processes to grow LEDs
on substrates that offer some advantages
compared to the well-established sapphire
substrates,” says Trifortune’s technical head Dr
Hu. “To compete in the HB-LED market, there is a
real need to achieve the maximum yield in our
manufacturing process, so that products with
better performance in lumen per dollar can be
established. The AIX G5 HT system is widely
acknowledged as having the top yields in LED
mass production, along with excellently
repeatable performance at high growth rates,” he
comments.
“We are very pleased to contribute to Trifortune’s
success and to share our comprehensive expertise
in optimization of epitaxy yields with them,” says
Aixtron’s chief technology officer Andreas
Toennis.
Read more
Altatech’s Orion LedMax wafer inspection and
metrology system chosen by LED maker Osram
Semiconductor Today
Altatech of Montbonnot, near Grenoble, France (a
subsidiary of Soitec since January 2012) has
received an order for its Orion LedMax wafer
inspection and metrology system from Osram
Opto Semiconductors GmbH of Regensburg,
Germany.
Osram will use the tool to improve the
performance, cost efficiency and yield of its LED
processing operations. Suitable for both volume
manufacturing and R&D applications, the
inspection system will perform production control
and new product qualification of Osram’s epitaxial
wafers used in fabricating LEDs.
Capable of inspecting wafers from 4-inches to 8inches in diameter, the Orion system combines
the diverse capabilities of 2D inspection, defect
height measurement and dark-field inspection in
one platform, producing what are claimed to be
the industry’s most thorough wafer-metrology
results. The tool generates more information than
just diffracted light signature, identifying
potentially
critical
defects
amid
noisy
backgrounds, providing superior matching
performance and reducing maintenance costs, it is
claimed.
Orion offers the full range of inspection and
metrology
capabilities
for
front-end
manufacturing process flows including incoming
wafer qualification, process development and line
monitoring. Proprietary Orion modules are
designed to conduct front-side and back side
surface inspection, edge inspection, bump and
through-silicon via (TSV) metrology by detecting,
counting and classifying defects on patterned and
unpatterned wafers.
Read more
The LED Patent Landscape
All LED Lighting
Philips and Cree by one criterion hold the highestquality LED patent portfolios, while Samsung and
LG have the raw numbers.
Intellectual property consultancy iRunway has
issued a preliminary report surveying the ground
of patents held by the top IP players in the LED
domain, with an emphasis on lighting. The PDF is
freely downloadable.
The majority of the 22,262 patents that iRunway
identified were filed within the last five or ten
years. While the report breaks down the issued
patents to three levels of categories, we will be
looking at overall numbers. The important
distinction we'll maintain is that between the total
number of patents a company holds, and the
number of "seminal" patents.
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patenting practices have matured even before the
technology itself has."
Read more
ELECTRONICS
RFMD awarded $9.7m Air Force contract to
produce first 6" mm-wave GaN-on-SiC Ics
Semiconductor Today
The table lists these overall numbers. The top 15
patent-holding organizations account for over 25% of
all patents issued for LED technology and applications.
Seminal patents
Samsung and LG lead in total numbers of patents,
but many of these are in areas touching on display
and backlighting, not general lighting. Both of
these consumer electronics giants turned their
attention to lighting only in the last few years.
Lately Samsung has been granted around 100
patents per year. Many of Philips's patents come
by way of Lumileds (sponsor of this site), whose
roots go back four decades under Hewlett
Packard. Cree began patenting LED technology in
the late 1980s.
Contention
A table on page 21 of the iRunway report
summarizes who has been suing whom in the LED
domain since 2011. Osram and Philips lead the
roster, both as plaintiff and as defendant, being
involved in 10 and 9 lawsuits respectively. On
average the six companies -- Cree, GE, LG, Osram,
Philips, and Samsung -- have been embroiled in six
court challenges each.
Considering all this activity and the considerable
number of licensing and cross-licensing deals that
have resulted from earlier struggles iRunway
concludes, "By all appearances, the LED industry's
RF Micro Devices Inc of Greensboro, NC, USA has
signed a $9.7m agreement with the
Manufacturing and Industrial Technologies
Directorate within the US Air Force Research
Laboratory (AFRL) to transfer and produce a
0.14μm gallium nitride (GaN) monolithic
microwave integrated circuit (MMIC) technology.
The technology will be scaled to 6”-diameter
wafers using RFMD’s 6” GaN-on-silicon carbide
(SiC) manufacturing line.
“Through this Air Force contract we have the
opportunity to establish the industry’s first 6-inch
millimeter wave GaN-on-SiC process technology,
allowing RFMD to expand our technology
capabilities beyond 100GHz,” says Gorden Cook,
general manager of RFMD Power Broadband. “We
expect this new technology will not only enable a
new class of affordable power MMICs for defense
applications such as radar and military
communications, but also commercial applications
including cable TV networking, microwave
backhaul and cellular infrastructure.”
According to industry analyst firm Strategy
Analytics, the GaN microelectronics market is
expected to more than triple to $334m by 2017,
representing a compound annual growth rate
(CAGR) of 28%, driven by both military (radar,
electronic
warfare,
communications)
and
commercial (power management, cellular, CATV,
land mobile radios) applications.
“AFRL has a distinguished history of developing
high-performance
technologies
with
an
understanding of underlying physics that drive
reliability,” says Cook. “RFMD plans to leverage
AFRL’s experience to offer reliable, 0.14μm-gate
GaN power technology for mass production in our
US-based, open foundry.”
GaN technology supports broad frequency
bandwidths and high breakdown voltages in a
small area. RFMD’s 6” GaN wafer offers 2.5-times
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more usable area over competing 4” GaN wafer
platforms currently available, resulting in 2.5
times more RF power devices per wafer.
Millimeter-wave GaN enables the best trade-off
between key performance parameters such as
power gain, bandwidth and efficiency for
applications in the range of DC to over 100GHz,
says RFMD."
Read more
EPC presenting DC-DC converter using eGaN
HEMTs operating at 10MHz with 89% peak
efficiency and ability to operate in harsh
environments
Semiconductor Today
At the 39th annual Government Microcircuit
Applications and Critical Technology (GOMACTech
2014) conference in Charleston, SC, USA (3 April),
Alex Lidow, CEO & co-founder of Efficient Power
Conversion Corp (EPC) of El Segundo, CA, USA,
which makes enhancement-mode gallium nitride
on silicon (eGaN) power field-effect transistors
(FETs) for power management applications, will
present results of a newly released family of eGaN
high-electron-mobility
transistors
(HEMTs)
designed for high-frequency operation in the
10MHz range. The presentation will also highlight
the stability of the devices under radiation
exposure, making them suitable for high-reliability
applications.
Enhancement-mode GaN transistors have been
commercially available since 2010. They have
since enabled significant efficiency improvement
in commercial DC-DC converters in a variety of
topologies and at a variety of power levels. Emode transistors have also demonstrated
tolerance to gamma radiation and single event
effects (SEE). Compared with radiation-tolerant
power MOSFETs, GaN FETs offer improvements of
up to a 40-fold in key switching performance
figures of merits, says EPC. This enables designers
of space-level power supplies to achieve the
efficiencies of commercial state-of-the-art
systems, the firm adds.
“These GaN-on-silicon power transistors, designed
for
multi-megahertz
switching
converter
applications, allow the designer of radiationtolerant systems to achieve power densities and
efficiencies that equal the commercial state-ofthe-art,” says Lidow.
Read more
EPC introduces development board for highcurrent,
high-stepdown
buck
converter
applications
Semiconductor Today
Efficient Power Conversion Corp (EPC) of El
Segundo, CA, USA, which makes enhancementmode gallium nitride on silicon (eGaN) power
field-effect transistors (FETs) for power
management applications, has introduced the
EPC9016 half-bridge development board for highcurrent,
high-stepdown-voltage,
buck
intermediate bus converter (IBC) applications
using eGaN FETs. In this application two low-side
(synchronous rectifier) FETs are connected in
parallel, since they will be conducting for a much
longer period compared to the single high-side
(control) FET.
EPC says that eGaN FETs have superior currentsharing capability compared with silicon MOSFETs,
making them suitable for parallel operation. This
development board expands upon EPC’s work on
optimal layout based on ultra-low inductance
packages. The optimum layout techniques that are
used increase efficiency while reducing voltage
overshoot and electromagnetic interference
(EMI).
The EPC9016 development board is a 40V
maximum device voltage, 25A maximum output
current, half-bridge featuring the EPC2015 eGaN
FET with an onboard LM5113 gate driver. The halfbridge configuration contains a single top-side
device and two parallel bottom devices and is
recommended for high-stepdown-ratio buck
converter applications such as point-of-load
converters and buck converters for non-isolated
telecom infrastructure.
The development board is 2” x 1.5” and contains
all critical components and layout for optimal
switching performance. There are also various
probe points to facilitate simple waveform
measurement and efficiency calculation.
EPC9016 development boards are priced at $130
each and are available from Digi-Key. A Quick Start
Guide is included for reference and ease of use."
Read more
KnowMade
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IQE delivers 200mm GaN-on-Si HEMT wafers to
Singapore-MIT LEES next-generation CMOS
program
Semiconductor Today
Epiwafer foundry and substrate maker IQE plc of
Cardiff, Wales, UK has delivered the first 200mm
(8”) gallium nitride-on-silicon wafers (GaN-on-Si)
into the Singapore-MIT Alliance for Research and
Technology Center’s Low Energy Electronic
Systems (SMART-LEES) program.
Despite the ever decreasing transistor linewidths
and highly complex architectures being deployed
by leading semiconductor companies globally,
conventional CMOS is now rapidly reaching
fundamental limits of silicon performance, notes
IQE. This has led to many foundries and integrated
device manufacturers (IDMs) actively developing
compound semiconductor on silicon (CSoS)
technologies in order to exploit the advantageous
electronic, optical and power handling properties
of compound semiconductors, while continuing to
use the scale and cost structure of existing silicon
semiconductor fabs, adds the firm.
The SMART-LEES program in Singapore is
developing (among other technologies) a
comprehensive array of CSoS technologies to
facilitate complete monolithic integration of
CMOS and compound semiconductor circuits, in a
way that allows the processing of wafers through
conventional 200mm CMOS processing lines. In
addition, design libraries will be developed to
allow widespread adoption of these technologies
across multiple end markets.
IQE has now delivered 200mm GaN-on-Si highelectron-mobility transistor (HEMT) wafers to this
program, which should enable the realisation of a
new generation of RF device architectures,
integrated with highly efficient power control
circuitry. It is expected that further collaboration
will quickly lead to a wide variety of other
compound semiconductor combinations to be
realised as part of the full array of CSoS
technologies.
“It has been clear for some time that conventional
CMOS is no longer capable of continuing Moore’s
law,” comments project leader Gene Fitzgerald,
the Merton C Fleming Professor of Materials
Science at MIT. “The ever increasing capital
intensity of narrowing linewidths, coupled with
the rapidly reducing performance benefit, means
a new paradigm needs to be introduced.
Compound semiconductors fully integrated on a
silicon platform is a highly optimal solution, taking
advantage of both the greatly superior
performance of compound semiconductors in
many applications, coupled with the cost benefits
of the existing silicon fab infrastructure,” he adds.
“Our program fully integrates III-V devices into the
silicon design platform, resulting in the ability to
develop fundamentally new circuit designs for a
wide-range of applications,” Fitzgerald continues.
The technologies will drive a new phase of growth
in the semiconductor industry, believes IQE’s
president & CEO Dr Drew Nelson. “Compound
semiconductors have always been the next
obvious choice to carry forward the silicon
industry, and we are very excited about being a
major part of the next revolution in fully
integrated CMOS technology, bringing the next
leap in performance across a great range of
technologies.”
Read more
MACOM announces IP licensing program and
supply deal with IQE for GaN-on-Si
Semiconductor Today
M/A-COM Technology Solutions Inc of Lowell, MA,
USA (which makes semiconductors, components
and subassemblies for analog, RF, microwave and
millimeter-wave applications) has announced an
IP licensing program that will make available its
gallium nitride on silicon (GaN-on-Si) technology
to select companies for use in RF applications.
MACOM detailed recent progress in two areas
critical to realizing its future vision of enabling the
mainstream adoption of GaN as a large-scale RF
semiconductor technology across the industry.
As a first step, MACOM has announced a license
and supply agreement that will enable IQE plc to
use its patent-protected technology to
manufacture GaN-on-Si epitaxial wafers at 4-, 6and 8-inch diameters in high-volume for RF
applications. This move is expected to enable
MACOM to deliver GaN RF products with
breakthrough bandwidth and efficiency at
mainstream 8-inch (200mm) silicon cost
structures, and to enable IQE to accelerate GaN
penetration into key target markets.
MACOM also says that it is in active discussions to
make GaN-on-silicon technology available to
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select companies for use in RF applications. The
firm believes that establishing such large-diameter
wafer manufacturing sources will be a key factor
in driving mainstream, commercial adoption of
GaN technology. Surety of supply is of critical
importance
in
power-amplifier-dependent
markets such as cellular base-stations, MACOM
reckons. According to market research firm
Strategy Analytics, power amplifier transistor
revenue from base-stations will grow to more
than $1bn in 2014.
“We are nearing a watershed moment for the RF
& microwave industry, promising breakthrough
performance for compound semiconductors and
leveraging large-scale silicon production facilities
that operate at orders-of-magnitude greater
economies of scale,” says MACOM’s president &
CEO John Croteau. “Our recent acquisition of
Nitronex and its portfolio of fundamental IP rights
related to GaN-on-silicon materials, process, and
device technology for RF applications provides us
with the foundation for a licensing program that
will help bring our vision of GaN performance at
mainstream 8-inch silicon cost structures a
reality,” he believes.
As the world’s biggest supplier of compound
semiconductor epitaxy (with the largest
independent manufacturing capacity), IQE
currently supplies over 50% of the world’s RF
epiwafers, and is already established as the
leading provider of GaN high-electron-mobility
transistor (HEMT) wafers for RF, broadband, and
military power amplifiers. IQE can hence achieve
enhanced economies of scale, says MACOM,
helping to build the wafer capacity and cost
structure needed to grow the GaN market.
Transistors for these applications have historically
been fabricated using 3 inch and/or 4-inch
(100mm) silicon carbide (SiC) substrates. To
complement these products and increase market
reach, IQE has developed and demonstrated
growth of GaN HEMTs on industry-standard silicon
substrates at wafer diameters of 100mm, 150mm
and 200mm. IQE reckons that this technology,
along with the comprehensive IP portfolio
licensed from MACOM, will enable tremendous
economies of scale, wafer capacity, and cost
structure needed to advance the GaN market.
“We are beginning to see very significant traction
for GaN occurring in the compound
semiconductor industry, across a wide range of
applications,” comments IQE’s president & CEO
Drew Nelson. “Our agreement with MACOM
allows us to further penetrate this new market by
bringing decades of high-volume production
experience to create the necessary supply chain
needed to accelerate GaN adoption,” he adds.
“Combining GaN HEMT performance with lowcost and large diameter silicon substrates enables
these wafers to be processed through existing
high-volume silicon factories. Commercial
availability of GaN HEMTs on 150mm and 200mm
wafers represents a significant milestone toward
the widespread adoption of this technology... We
have already delivered MACOM 200mm diameter
GaN-on-Si wafers, and we look forward to a
powerful ongoing relationship,” Nelson continues.
”This partnership achieves a critical milestone in
the mainstream commercializatin of GaN
technology by establishing the manufacturing
capability and capacity required to bring reliable,
high-volume surety of supply to the industry,”
believes Croteau.
Read more
Raytheon demonstrates GaN-on-diamond HEMT
with 3x increase in power density over GaN-onSiC
Semiconductor Today
Raytheon Company of Waltham, MA, USA says
that it has achieved another milestone for nextgeneration gallium nitride (GaN) radio-frequency
(RF) semiconductor technology. Through the US
Defense Advanced Research Projects Agency
(DARPA) Near Junction Thermal Transport (NJTT)
effort under the Thermal Management
Technologies program, Raytheon’s team is
replacing GaN’s current substrate silicon carbide
(SiC) with diamond, a material with 3-5x higher
thermal conductivity, to create GaN-on-diamond
devices.
Raytheon has demonstrated that GaN-ondiamond technology enables a 3x increase in
transistor power density over GaN-on-SiC,
overcoming a major barrier to unlocking the
potential of GaN devices, it is reckoned. Data was
obtained on a 10 x125μm GaN-on-diamond highelectron-mobility transistor (HEMT), a device
representing a unit cell for constructing power
amplifier monolithic microwave integrated circuits
KnowMade
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(MMICs), which are the foundation of solid-state
RF transmitters and active electronically scanned
arrays (AESAs). Raytheon says that this lattest
result builds on prior successes, including its
industry-first demonstrations of GaN-on-diamond
transistors in 2009 and of GaN-on-diamond
MMICs in 2011.
“We are now inserting GaN into DoD systems
while remaining focused on continuing to increase
performance of this revolutionary semiconductor
to provide our warfighters with the most
advanced sensing, communications and electronic
warfare capabilities in the world,” says Joe Biondi,
VP of Advanced Technology for Raytheon’s
Integrated Defense Systems (IDS) business in
Tewksbury, MA.
GaN-on-diamond
offers
performance
improvement by reducing thermal resistance
within the device and enabling GaN to be used at
higher power densities, which can dramatically
reduce the cost, size, weight and power of
defense systems, says Raytheon. GaN is a core
competency within Raytheon and an integral
technology behind some of the its major
programs, including the US Navy’s Air and Missile
Defense Radar program (AMDR) and the Next
Generation Jammer (NGJ) program. GaN’s unique
qualities allow radar, electronic warfare and
communications systems to be smaller, more
affordable and highly efficient, says Raytheon.
Raytheon also recently announced that, under the
DARPA Microsystems Technology Office (MTO)
Wide Bandgap Semiconductor (WBGS) program, it
has systematically matured GaN from basic
material to transistors, MMICs, transmit/receive
(T/R) modules and finally transmit/receive
integrated multi-channel modules (TRIMMs).
Read more
OTHER
Ammono and Unipress devise fast, low-cost
production of ammonothermal GaN
Semiconductor Today
Ammono S.A. in Warsaw, Poland, which produces
bulk gallium nitride (GaN) using ammonothermal
technology, and the Institute of High Pressure
Physics of the Polish Academy of Sciences
(Unipress) say they have conceived proprietary
new technology that allows cheap and fast
production of ammonothermal GaN on the basis
of hybrid Ammono-HVPE GaN seeds.
Ammonothermal gallium nitride is seen as a
perfect material for performance-driven electronic
and optoelectronic applications, which require
very good crystal quality, says Ammono. An
example is the laser diode, where output power
and lifetime depend strongly on GaN substrate
quality. Other examples are power transistors and
Schottky diodes, where reliability is related
primarily to the device’s crystalline structure and
thus substrate quality. Last but not least, ultrahigh-brightness LEDs benefit tremendously from
the substrate’s low dislocation density, which
allows effective dissipation of the heat created
during device operation.
Competing GaN production technologies such as
hydride vapour phase epitaxy (HVPE) or liquid
phase epitaxy (LPE) use foreign (non-GaN) seeds,
and the quality of the GaN material obtained in
this way results in the manufacture of devices
that, on a long-term scale, do not achieve the
quality targets set by device makers, claims
Ammono. This lower quality is reflected in many
parameters, most importantly the dislocation
density, which in the case of ammonthermal GaN
is of the order of 104cm-2 whereas other
technologies are at least two orders of magnitude
worse, adds the firm.
Ammono and Unipress have shown that using
hybrid HVPE-ammonthermal approaches allows
the manufacture of GaN material fulfilling the
strict requirements of high-end applications. In
the framework of a grant received from the Polish
National Center for Research and Development
(PBS1/B5/7/2012) it was shown that, by using
ammonothermally grown GaN (as a seed), one can
obtain high-quality free-standing HVPE-GaN (for
details, see Appl. Phys. Expri 6, 075504 (2013)).
Smooth GaN layers up to 2.5mm thick (crystallized
with a stable growth rate of 240μm.hr-1) and of
an excellent crystalline quality, without cracks,
and with low threading dislocation density (5x104
cm-2) have been grown and then sliced from the
Ammono-GaN seed wafers (see Figure).
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Gallium nitride device and substrate market to
rise to $15.6bn by 2022
Semiconductor Today
The structural properties of the free-standing
HVPE-GaN do not differ from the structural
properties of the Ammono-GaN seeds, notes the
firm. Additionally, this is a high-purity material.
According to the SIMS analysis the oxygen and
carbon content is below 1016cm-3. The only
silicon impurity is of the order of 3x1016cm-3.
Thus, from the point of view of physical
properties, the HVPE-GaN is of a much higher
quality than the that obtained using MOCVDGaN/sapphire templates or GaAs crystals as seeds,
it is claimed.
Subsequently, the new material was used again as
a seed for the ammonthermal process. As a result,
a new kind of GaN crystal was grown (AmmonoHVPE-Ammono). Their characteristics were
presented for the first time during the Gallium
Nitride Materials and Devices IX conference at
SPIE’s Photonics West 2014 event in San
Francisco. A threading dislocation density of
2x105cm-2 and average full width at half
maximum (FWHM) of 19 arcsec define the new
ammonothermal material as top class compared
with other existing GaN manufacturing
approaches, claims Ammono.
The new proprietary and patent protected
technology allows high-volume, high-quality GaN
seed replication, which will accelerate the spread
of ammonthermal GaN to mass-market
applications, the firm reckons. It will also allow
Ammono-GaN production costs to be driven down
in an aggressive way due to much faster
availability of a vast population of high-quality
GaN seeds, it concludes.
Read more
According to the report ‘Gallium Nitride (GaN)
Semiconductor Devices (Discrete & IC) and
Substrate Wafer Market by Technology,
Application, Product, Device, & by Geography Forecast & Analysis to 2013–2022’ from
MarketsandMarkets, the market is forecasted to
reach $15.6bn by 2022.
In particular, the specific sub-sector where GaN
has an edge over established silicon-based
counterparts is ‘Power Semiconductors &
Electronics’. In terms of end-user applications, the
two major upcoming sectors driving demand for
GaN devices are the Industrial & Power sector and
Communication Infrastructure sector. The
Communication Infrastructure sector has found
use for GaN power discretes, particularly
transistors in power amplification, rectification,
and high-frequency switching.
GaN has turned out to be the technology of choice
for most power semiconductor applications and is
quickly replacing the existing silicon technology,
reckons the report. Compared with pure silicon
devices, the various properties of GaN such as a
wider bandgap energy, high breakdown voltage,
larger critical electric field, and higher thermal
conductivity allow GaN devices to operate at
higher voltages and high switching frequencies,
and to handle higher power density, offering
enhanced power efficiency.
These properties allow GaN discretes such as
Schottky diodes, FETs, HEMTs and the other
advanced transistors to operate efficiently at
much higher voltage levels, exceeding the limits of
their counterpart silicon devices.
GaN power semiconductors also help to reduce
conduction and switching losses, offering higher
efficiency in electronic systems. Currently, the
major application segments of GaN power
semiconductors are inverters (& converters), RF
devices, power supply modules, and motor drives,
used across all end-user sectors.
The GaN power semiconductor device market is
growing primarily due to penetration into the
medium-voltage power electronics market and
applications across all major end-user verticals. It
is obvious that most revenue comes from the
rising number of advanced power applications in
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the industrial, power, solar and wind sector and
the sector's developing globally. GaN power
devices draw most of their revenue from the
Communication Infrastructure sector, focusing
solely on replacing their silicon counterparts in
various RF power devices, particularly in RF
communication applications over the past few
years.
Regarding their features, GaN devices are smaller
and lighter but tougher and more efficient than
silicon devices, and can serve as replacements for
their silicon counterparts, which have hit maturity.
GaN devices and wafers also feature low
sensitivity to ionizing radiation, and better stability
in some radiation environments. They also have a
future in solar cell arrays, satellites and high-end
power appliances in the Military, Defense &
Aerospace sector.
These devices also have huge revenue potential in
the automotive and transportation sector, mainly
in electric vehicles & hybrid electric vehicles
(EV/HEV).
Since GaN power semiconductors have the
potential to operate at higher temperatures,
higher power levels and voltages, and high
frequencies (microwave ranges), the number of
applications is increasing continuously in various
industries,
including
telecommunications,
consumer electronics, automotive, industrial,
power and clean-tech applications.
Currently, GaN accounts for less than 1% of the
total power semiconductor market (which
currently amounts to $34bn, including power
discrete and power ICs). However, over the next
ten years, the entire base for power
semiconductors & electronics players is expected
to penetrate into this new value chain, rapidly
increasing the percentage share.
In particular, the GaN market's total competitive
landscape had only a handful of players at the
beginning of the last decade but quickly emerged
into a significant network of key players for both
power and optoelectronic semiconductor devices.
Companies cited in the report include Aixtron SE,
Azzurro Semiconductors AG, Cree Inc, Epigan NV,
Fujitsu Ltd, International Quantum Epitaxy (IQE)
plc, Koninklijke Philips N.V., Mitsubishi Chemical
Corp, Nippon Telegraph & Telephone, RF Micro
Devices Inc, Texas Instruments Inc, Toshiba Corp.
Today's world includes many suitable power
applications for GaN in several segments, such as
power distribution systems, industrial systems,
heavy electrical systems, turbines, heavy
machinery, advanced industrial control systems,
electro-mechanical computing systems etc, as well
as several new power applications (clean-tech)
including high-voltage direct current (HVDC),
smart grid power systems, wind turbines, wind
power systems, solar power systems, and electric
& hybrid electric vehicles. Another application
sector is ICT, with several communication
application segments such as RF, radar, and
satellite communications offering huge revenue
potential due to the unbeatable ability of GaN to
operate at high-frequency ranges (including
microwave frequencies). The potential size of
these markets is currently in the trillions, it is
reckoned, making the total addressable market for
GaN power semiconductors worth billions.
Read more
IP battle expected in next three years as GaN-onSi enters production
Semiconductor Today
GaN-on-Si technology has emerged naturally as an
alternative to GaN-on-sapphire — the mainstream
technology for LED applications. But today,
despite potential cost benefits, the mass adoption
of GaN-on-Si technology for LED applications
remains unclear, notes market research firm Yole
Développement. Most major LED makers have a
patenting activity related to GaN-on-Si technology
but, so far, few have made it the core of their
strategy and technology roadmap. In contrast to
the LED industry, Yole expects GaN-on-Si to be
widely adopted by power electronics and RF
applications because of its lower cost and CMOS
compatibility.
The growth of GaN-on-Si substrate was first
reported in the early-1970s (T. L. Chu et al., J.
Electrochemical Society, Vol. 118, p1200). Since
the early 1990s, an increasing number of
academics and industrial concerns have been
involved in developing the technology. GaN-on-Si
is now poised to meet a series of technical
challenges. The high lattice mismatch between
GaN and silicon results in a high density of defects
(specifically, dislocations) in epitaxial layers. The
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high mismatch in the thermal coefficient of
expansion (TCE) between GaN and silicon leads to
a large tensile stress during cooling from the
growth temperature to room temperature. The
tensile stress can cause film cracking and concave
bending of the wafer (warpage). These factors
combine to make the reduction of both
dislocation density and cracking/warpage a
challenge.
Knowmade’s patent investigation covers patents
published worldwide up to December 2013. The
patents
addressing
the
above-mentioned
challenges have been selected, and an in-depth
analysis of patent holders and corresponding
patented technologies has been conducted. The
report does not include patents related to active
layers or GaN-based devices.
Fundamental patents describing a GaN-based
compound semiconductor grown on a silicon
substrate were filed before the 1990s, with the
most significant assigned to Japan’s TDK and
Fujitsu. In the early 1990s, Toyoda Gosei and the
University of Nagoya filed the first concepts of a
buffer layer for improving GaN crystallinity. Those
fundamental patents have been followed by an
ever increasing number of applications since 1995
as more companies competed in GaN-on-Si
technology to meet the technical challenges and
market demand, and to reduce manufacturing
costs. Currently, the patented technologies reflect
the significant improvements that have been
made on key material issues such as dislocation
density reduction and stress management for
preventing cracking and warpage of the wafer.
According to Knowmade’s analysis, GaN-on-Si
intellectual property (IP) is mature enough to
initiate mass production.
Define your patent strategy with deep patent
segmentation and a useful database
Knowmade’s search strategy combines automated
and manual screenings that have led to the
selection of more than 560 relevant patent
families. Those have been manually segmented by
type (epitaxial layer, layer transfer) and organized
in various technology segments that are analyzed
in detail: defect reduction (ELOG, pendeoepitaxy,
nanomasking, defect selective passivation etc),
stress management (AlN-based interlayer, buffer
engineering, patterned substrate, compliant
substrate, etc), and buffer type (Al-containing
single layer, compositionally graded AlGaN,
superlattices, etc). For each segment, the report
provides an analysis including the time evolution
of patent filings, and identification of the key
players and collaboration networks. More than 60
key patents have been identified on the basis of
several indicators (family size, legal status,
citations analysis, and impact in GaN-on-Si
technology etc).
Key players and new IP challengers
More than 50 companies and academics are
involved in GaN-on-Si IP, and most of the major
GaN players are present in the list of the top
patent applicants. Toyoda Gosei, Toshiba,
Panasonic, Mitsubishi, Nitronex, Soitec, and
Azzurro have strong IP portfolios related to GaNbased epitaxial layers on silicon, but Samsung,
Dowa, LG, Sharp and NGK Insulators are becoming
major forces in the GaN-on-Si IP landscape. Soitec
and Sumitomo lead in patent filings related to
GaN layer transfer onto silicon substrate.
The report provides a ranking and analysis of the
relative strengths of the top GaN-on-Si patent
holders derived from their portfolio size, patent
citations networks, countries of patent filings, and
current legal status of patents. Based on this
portfolio analysis, Knowmade has identified 15
major players profiled by the report, including a
portfolio summary with patenting activity,
patented technologies, key patents, granted
patents near expiration, partnerships, and IP
strength and strategy.
Future of GaN-on-Si IP
Currently, there are just a few players selling
either epiwafers or template wafers - or both - on
the open market. The number of commercial GaNon-Si device makers is also limited. Apart from a
few
noticeable
IP
collaborations
(Nitronex/International
Rectifier,
Toshiba/Bridgelux,
Soitec/Sumitomo,
MACOM(Nitronex)/IQE), GaN-on-Si IP has not yet
been widely used by companies as leverage to
negotiate licensing and supply agreements, says
Knowmade. So far, only a few cases of litigation
have been observed.
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46
However, the existing IP covers all subjects related
to the technical challenges, and the last five years
have seen a reinforcement of critical patent filings
by major GaN players (Toshiba, Samsung, LG,
Sharp, NGK, Sumitomo, Soitec, Azzurro and
Dowa). Furthermore, the GaN-on-Si industry is
beginning to take shape, as evidenced by the
recent interest of RF/power industry players in
GaN-on-Si technology (e.g. the acquisition of
Nitronex by MACOM) and the desire of several
firms to move to the production stage (Toshiba,
Samsung etc). An IP battle should hence be
expected in the next three years, concludes
Knowmade and Yole Développement."
Read more
“With an increased competition in the MOCVD
industry, the leaders are still getting most of the
equipment business in a recovering LED frontend
equipment
market”,
says
Yole
Développement
Semiconductor Today
“Following the strong growth of the LED TV
market in 2010, the MOCVD industry competition
increases. But, today, we still do not see any
impact on the market structure … The 3 leaders
are still there for a long time.”, explains Pars
Mukish, Senior Analyst, LED at Yole
Développement. Yole Développement announces
this week its new LED report dedicated to frontend equipment market. Under this report, Yole
Développement’s analysts give a better
understanding of the LED front-end manufacturing
technical trends. They describe the supply chain
and each related process steps. They also details
key players and their positioning in this industry.
LED Front-End Equipment Market report includes
market metrics from 2014 to 2019 at both LED
devices and material/equipment levels.
LED epitaxy equipment market has always been of
central interest to equipment manufacturers due
to its high average selling price (ASP), strong
profitability, and large market volume (compared
to other equipment markets).
“Since 2010, more than 20 players (mostly from
Asia) have tried to enter the MOCVD reactor
market but without real success: in 2013, these
new suppliers represented only 3% of market
share (only +2% compared to 2010)”, explains Pars
Mukish, Yole Développement.
This situation arises for two main reasons:
 New entrants have missed the first 2 LED
growth cycles (small display and large display
applications) that have allowed leaders to build
their expertise and know-how as well as their
networks (sales office, training center…). Even
big names, such as Applied Materials, did not
achieve access to these markets.
 Revenue collected during the 2010-2011
investment cycle (a total of more than $2
billion for MOCVD reactors, with > 90% going
to Aixtron and Veeco) have allowed Veeco and
Aixtron to slash ASP and initiate a price war to
lever further market entry barriers.
The current LED front-end industry is largely
driven by cost reduction (as technological
evolutions are reaching their saturation point).
The main strategy developed by a new MOCVD
reactor supplier is to focus on decreasing cost of
ownership through a new heating system, new gas
flow design, and increased automation (…).
However, even if this is the best and only strategy
to adopt, we do not expect new entrants to have a
big increase in future market share as the finances
and expertise of the Big 2 far surpass any of their
competitors.
At short term, only two types of suppliers (outside
of the Big 3) will survive:
 Suppliers that develop collaboration with some
big LED manufacturers.
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 Chinese suppliers that are able to scrape
together bits and pieces of the huge local
market.
Under this report, Yole Développement presents a
detailed analysis of the LED MOCVD reactor
industry, detailing key players but also new
entrants. It also highlights new strategies
developed by these new entrants, future
evolution of the industry …
Read more
IQE’s revenue and profits rise strongly, driven by
robust wireless business and diversification
Semiconductor Today
For full-year 2013, epiwafer foundry and substrate
maker IQE plc of Cardiff, Wales, UK has reported
record revenue of £126.8m, up 44% on 2012’s
£88m (despite an adverse second-half currency
impact as sterling appreciated 3% against the US
dollar). However, this includes £30.9m from Kopin
Wireless (the MOCVD-based HBT epiwafer
manufacturing business of Kopin Corp of Taunton,
MA, USA, acquired in January 2013).
For second-half 2013 (compared with first-half
2013, on a constant currency basis), wireless sales
were up 3% and photonic sales were up 12%.
“IQE’s core wireless division has again delivered a
robust performance, with continued growth
despite a significant downstream inventory
correction in the major chip companies due to
softness in the high-end smartphone market,”
says chief executive Dr Drew Nelson. “As a direct
result of our customer risk mitigation strategy,
which we have executed over the last 18 months
and completed with the acquisition of Kopin
Wireless, we are much less sensitive to market
share shifts between the major chip supply
companies,” he adds.
For full-year 2013 compared with full-year 2012,
adjusted profit before tax (PBT) was up 51% from
£8.6m to £13m. Adjusted fully diluted earnings
per share (EPS) was up 43% from 1.4p to 2p. Cash
inflow from operations (before exceptional items)
was up from £4.7m to £16.2m. Cash conversion
has more than doubled, from 51% to 111%. During
second-half 2013, net debt rose from £15.5m to
£34.4m, but this was due primarily to £25m of
debt to part fund the Kopin acquisition.
IQE says that the integration of Kopin Wireless has
been reflected in strong operational performance
and major customer service awards. In particular,
operational efficiency has improved through the
benefit of synergies including sharing best practice
and economies of scale. The firm is on track to
eliminate duplicate overheads through the
consolidation of operations without any loss of
capacity or technology, saving more than £7m on
an annualised basis.
“Concerns in the UK over the last year that silicon
CMOS would significantly damage the compound
semiconductor industry have proved unfounded
and are not reflected in our financial performance
nor in our customers’ expectation of future longterm demand drivers,” says Nelson.
“Wireless remains an attractive market for us over
the coming years, with demand continuing to be
driven by the proliferation of wireless applications
and the need for sophisticated GaAs chips to deal
with the explosive growth in data traffic,”
continues Nelson. “Beyond this, the next waves of
innovation which will drive handset-replacement
cycles are likely to include lasers and sensors using
compound semiconductor technology, for gaming,
3D image capture, gesture recognition, and
sensing for a variety of applications including
healthcare monitoring devices,” he adds.
“Our business diversification strategy also gained
strong traction, and we achieved a number of
significant technical and commercial milestones
during 2013 which reflect the strong progress
made in our other key markets including photonic
sensors and lasers, advanced solar (CPV), power
semiconductors, infrared, LED and advanced
electronics,” says Nelson.
IQE notes that its concentrated photovoltaics
(CPV) commercialization strategy has been
strengthened by the acquisition this month of its
stake in CPV cell maker Solar Junction Corp (SJC)
of San Jose, CA, USA by a strategic investor. In
particular, a robust supply chain is being
established and qualification is progressing well,
says IQE.
IQE says it is making progress on its diversification
strategy through new product development and
qualifications, including:
 a major three-year supply contract with Philips
for vertical-cavity surface-emitting laser
(VCSEL) applications (announced last October);
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 a new 150mm VCSEL product for high-volume
applications (launched in mid-March);
 the achievement of record VCSEL energyefficiency and speed performance (announced
in February and March, respectively);
 the development of silicon photonics
technology (reported in late January); and
 the world’s first 150mm indium antimonide
(InSb) substrates for infrared applications
(launched at Photonics West 2014 in February);
IQE states that the reorganization of its business
into market streams reflects confidence of strong
growth in emerging markets and revenue
diversification.
“IQE is at the forefront of the enabling
technologies that are at the very heart of many of
the 21st-century trends and products,” says
Nelson. “We are confident that the group is well
positioned for continued growth in earnings and
cash flow in 2014 and beyond.”"
Read more
Hittite To purchase keragis assets - The
acquisition will enable Hittite to provide high
power gallium arsenide and gallium nitride
wideband amplifiers
i-micronews
Hittite Microwave Corporation has entered into a
definitive agreement to buy substantially all the
assets of Keragis Corporation.
Keragis is a provider of high power, wideband
amplifier modules, located in San Diego,
California.
The purchase price was not disclosed.
This acquisition expands Hittite’s power amplifier
(PA) portfolio and capabilities. This union
combines Hittite’s capabilities of design and
manufacture of high performance integrated
circuits (ICs), modules and subsystems with
Keragis’ patented wideband high power amplifier
module products.
“Keragis’ power amplifiers in combination with
Hittite’s semiconductor technologies, synthesizer
and up/down converter module portfolio will
allow Hittite to expand its system content in both
military and commercial applications that include
electronic warfare, radar, communications, and
test equipment,” says Rick Hess, President and
CEO of Hittite.
Keragis’ PAs use both GaAs and GaN
semiconductor technologies.
The closing of the transaction is expected to occur
within the next 90 days.
Read more
SAMCO
to
distribute
Valence
Equipment’s MOCVD systems
Process
Semiconductor Today
Valence Process Equipment Inc (VPE) of
Branchburg NJ, USA has signed an agreement for
SAMCO International of Kyoto, Japan to distribute
its metal-organic chemical vapor deposition
(MOCVD) equipment. The agreement gives
SAMCO exclusive distribution rights in Japan as
well as non-exclusive rights to sell the products in
other areas including China, South Korea and
Europe.
VPE has developed a novel MOCVD reactor for
gallium nitride (GaN)-based devices including
high-brightness LEDs for solid-state lighting. The
system’s unique, patented design reduces
consumption of expensive gases and metalorganic precursors by up to 40% in comparison
with competing products, the firm claims. VPE’s
initial product was the GaN-500 reactor,
announced in 2011, with a current capacity of
59x2” or 18x4” wafers. The firm recently released
the GaN-550 MOCVD reactor, with a capacity of
72x2” or 20x4” wafers.
SAMCO is an established provider of dry etch,
plasma CVD and surface treatment systems for
compound semiconductor applications, including
wide-bandgap materials (e.g. for RF devices, LEDs
and laser diodes). While gaining market share in
Japan, it is expanding its sales in Europe and North
America.
Recently, SAMCO placed a focus on selling nextgeneration production equipment for GaN power
devices. The addition of MOCVD strengthens
SAMCO’s product line-up, as MOCVD, plasma CVD,
dry etching and surface treatment systems can be
bundled to provide a ‘on- stop solution’ for users
involved in GaN semiconductor applications.
As part of the agreement, SAMCO will purchase
and install a GaN-550 MOCVD system in its facility
in Kyoto for customer demonstrations. Installation
is planned for July and the system will be used to
develop novel power device epitaxial structures
KnowMade
49
on large-diameter wafers in collaboration with a
key customer.
“We are delighted to embark on this partnership
with a highly respected and capable company like
SAMCO,” comments VPE’s CEO & founder Frank
Campanale. “Our MOCVD system complements
SAMCO’s existing product range and creates a
unique suite of products for the GaN
semiconductor community”.
Read more
Riber makes profit in 2013 despite revenue
falling 14%
Semiconductor Today
After reporting revenue for full-year 2013 in late
January, Riber S.A. of Bezons, France, which
manufactures molecular beam epitaxy (MBE)
systems as well as evaporation sources and
effusion cells, has now reported its full earnings
figures.
Revenue was €23.5m for 2013, down 14% on
2012’s €27.4m. Of this, MBE system revenue of
€16.9m was down 13% on 2012’s €19.4m. No
production machines were sold in 2013
(compared with 2 in 2012). However, this was
partly offset by sales of systems to research
customers rising from 15 in 2012 to 17. Riber says
that, during the past year, it has further
strengthened its positions in research markets in
order to limit the significant downturn affecting
industrial markets due to their current excess
capacity.
Revenues from services and accessories (€5.3m,
down 13% from €6m) and cells and sources
(€1.3m, down 35% on €2m) are down 18% overall,
due primarily to the weak level of demand in 2013
from industrial customers. Sales of cells for new
markets - organic light-emitting diodes (OLEDs)
and thin-film solar - have remained sluggish,
pending the next wave of capacity investments in
South Korea. However, this decrease has been
limited by the development of sales of MBE
effusion sources to R&D customers.
Gross profit was €7.5m in 2013 (down 17% from
€9.1m), representing gross margin of 32.2% of
revenue (down only slightly from 33.2%). More
specifically, the 1-point drop in margin reflects the
provisioning for inventories, with a net charge of
€0.2m for 2013, compared with a €0.6m reversal
in 2012.
Also, operating expenses are down year-on-year,
notably benefiting from the policy rolled out by
Riber at the beginning of 2013 to reduce its fixed
costs. Hence, Riber still made a net income of
€0.2m (1% of revenue), albeit down from €1.9m
(7% of revenue) in 2012.
During 2013, cash reserves fell from €3.6m to
€1.7m, factoring in the high level of billing at the
very end of the year and the ramping up of
innovation efforts during the year. Despite a lower
level of business, the firm generated +€1.2m in
cash flow from operations in 2013.
In view of the results for 2013 and the
requirements for financing innovation, Riber’s
management board will not be submitting a
proposal for a dividend at the general meeting on
3 June.
At the end of February, order backlog was €7.4m
(up from €7m at the end of 2013), with six
research systems to be delivered from secondquarter 2014 and significant levels of orders for
services and accessories. The firm says that it is
currently seeing an increase in deals for the R&D
MBE market.
Riber says that in 2014 it is focusing its efforts on:
 promoting its new Compact 21 DZ R&D MBE
system;
 extending its range of MBE effusion sources,
and continuing to make gains in market share;
 developing thin-layer complex material
deposition equipment, particularly for the
buoyant OLED flat-screen sector;
 over the longer term, incorporating MBE into
the silicon manufacturing chain (for III-V on
silicon materials, etc).
Riber’s technological expertise, its presence in
South Korea, and the quality of its research
partnerships represent strong assets to support
these developments."
Read more
KnowMade
50
PATENT APPLICATION
More than 147 new patents were published between 2014-03-24 and 2014-04-20.
Patent Applicants
Number of new patents
Fujitsu
9
Toyoda Gosei
6
Epilight Technology
6
ITRI
5
Nanjing Univ.
4
Sumitomo
4
Toshiba
4
Inst. Of Microelectronics (Chinese Academy Of Sciences)
4
Samsung
3
Furukawa
3
Intel
3
Osram
3
Fuji Electric
3
International Rectifier
3
Transphorm, LG Innotek, OKI Electric Industry, HC Semitek, Infineon, Dowa, SaintGobain, Seoul Semiconductor, Sixpoint Materials, Soraa, TSMC, glo, Mitsubishi,
Hitachi, Sharp, Bosch, Canon, Imec, Renesas, Rohm, Sanken Electric, Covalent
Materials, Tekcore, Translucent …
New patent applications selected by Knowmade
Gallium nitride power devices
Vertical nitride-based light emitting diode
having ohmic contact pattern and method of
manufacturing the same
Publ. Nb: US2014103399
Patent Assignee: Transphorm (US)
Publ. Nb: US2014106483
Patent Assignee: Samsung (KR)
Enhancement mode III-nitride devices are
described. The 2DEG is depleted in the gate
region so that the device is unable to conduct
current when no bias is applied at the gate.
Both gallium face and nitride face devices
formed as enhancement mode devices.
Provided is a vertical nitride-based LED including
a first electrode; a first nitride semiconductor
layer that is disposed on the first electrode; an
active layer that is disposed on the first nitride
semiconductor layer; a second nitride
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semiconductor layer that is disposed on the
active layer; an ohmic contact pattern that is
disposed on the second nitride semiconductor
layer; a second electrode that is disposed on the
ohmic contact pattern; and a bonding pad that
is electrically connected to the second electrode
and disposed on the second nitride
semiconductor layer.
horizontal-direction growth region (320b)
comprising a nitride semiconductor spread in
the c-axis direction from each of the plurality of
crystal-growth seed regions, the interval (S
width) between adjacent crystal-growth seed
regions being at least 20 .mu.m.
Nitride semiconductor structure, laminate
structure, and nitride semiconductor lightemitting element
Publ. Nb: WO2014051761
Patent Assignee: Intel (US)
High breakdown voltage III-N depletion mode
mos capacitors
Publ. Nb: WO2014054284
Patent Assignee: Panasonic (JP)
A nitride semiconductor structure having an m
surface as a primary surface, wherein the
structure is provided with a plurality of crystalgrowth seed regions (130) comprising a nitride
semiconductor extending at an angle in a range
of 0-10deg. in relation to an a-axis, and a
III-N high voltage MOS capacitors and System on
Chip (SoC) solutions integrating at least one III-N
MOS capacitor capable of high breakdown
voltages (BV) to implement high voltage and/or
high power circuits. Breakdown voltages over
4V may be achieved avoiding any need to series
couple capacitors in an RFIC and/or PMIC. In
embodiments, depletion mode III-N capacitors
including a GaN layer in which a two
dimensional electron gas (2DEG) is formed at
threshold voltages below 0V are monolithically
integrated
with
group
IV
transistor
architectures, such as planar and non-planar
silicon CMOS transistor technologies. In
embodiments, silicon substrates are etched to
provide a (111) epitaxial growth surface over
which a GaN layer and III-N barrier layer are
formed. In embodiments, a high-K dielectric
layer is deposited, and capacitor terminal
contacts are made to the 2DEG and over the
dielectric layer.
KnowMade
52
Light-Emitting Diodes on Concave Texture
Substrate
Publ. Nb: US2014087505
Patent Assignee: TSMC (TW)
A semiconductor device having light-emitting
diodes (LEDs) formed on a concave textured
substrate is provided. A substrate is patterned
and etched to form recesses. A separation layer
is formed along the bottom of the recesses. An
LED structure is formed along the sidewalls and,
optionally, along the surface of the substrate
between adjacent recesses. In these
embodiments, the surface area of the LED
structure is increased as compared to a planar
surface. In another embodiment, the LED
structure is formed within the recesses such
that the bottom contact layer is non-conformal
to the topology of the recesses. In these
embodiments, the recesses in a silicon substrate
result in a cubic structure in the bottom contact
layer, such as an n-GaN layer, which has a nonpolar characteristic and exhibits higher external
quantum efficiency.
Normally-off high electron mobility transistor
Publ. Nb: EP2713402
Patent Assignee: Samsung Electronics (KR)
A normally-off high electron mobility transistor
(HEMT) includes: a channel layer (120) having a
first nitride semiconductor, a channel supply
layer (130) on the channel layer, a source
electrode (161) and a drain electrode (162) at
sides of the channel supply layer, a depletionforming layer (140) on the channel supply layer,
a gate insulating layer (150) on the depletionforming layer, and a gate electrode (170) on the
gate insulation layer. The channel supply layer
includes a second nitride semiconductor and is
configured to induce a two-dimensional
electron gas (2DEG) in the channel layer. The
depletion-forming layer has at least two
thicknesses and is configured to form a
depletion region in at least a partial region of
the 2DEG. The gate electrode contacts the
depletion-forming layer.
Group-III nitride semiconductor element and
method for manufacturing same
Publ. Nb: WO2014049885
Patent Assignee: DOWA Electronics Materials (JP),
Wavesquare (KR)
Provided is a high-quality group-III nitride
semiconductor element in which the generation
not only of x-shaped cracks extending from the
vicinity of a corner to the center portion of a
semiconductor structural part but also of dotshaped cracks occurring in the center section is
suppressed. Also provided is a method for
efficiently manufacturing said group-III nitride
semiconductor element. This group-III nitride
semiconductor element is characterized by
including a support body (146A) and two
semiconductor structural parts (114) provided
on the support body (146A), the shape of the
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lateral cross section of the semiconductor
structural parts (114) being substantially
quadrilateral. The two semiconductor structural
parts (114) are positioned so that one side
surface (150A) of one of the semiconductor
structural parts (114) faces one side surface
(150A) of the other semiconductor structural
part (114), and the support body (146A) covers
the remaining three side surfaces (150B, 150C)
of the four side surfaces of each of the
semiconductor structural parts (114).
Vertical microelectronic component
corresponding production method
and
Publ. Nb: US2014084299
Patent Assignee: Robert Bosch (DE)
AlN inter-layers in III-N material grown on
DBR/silicon substrate
Publ. Nb: US8680507
Patent Assignee: Translucent (US)
A DBR/gallium nitride/aluminum nitride base
grown on a silicon substrate includes a
Distributed Bragg Reflector (DBR) positioned on
the silicon substrate. The DBR is substantially
crystal lattice matched to the surface of the
silicon substrate. A first layer of III-N material is
positioned on the surface of the DBR, an interlayer of aluminum nitride (AlN) is positioned on
the surface of the first layer of III-N material and
an additional layer of III-N material is positioned
on the surface of the inter-layer of aluminum
nitride. The inter-layer of aluminum nitride and
the additional layer of III-N material are
repeated n-times to reduce or engineer strain in
a final III-N layer.
A vertical microelectronic component includes a
semiconductor substrate having a front side and
a back side, and a multiplicity of fins formed on
the front side. Each fin has a side wall and an
upper side and is separated from other fins by
trenches. Each fin includes a GaN/AlGaN
heterolayer region formed on the side wall and
including a channel region extending essentially
parallel to the side wall. Each fin includes a gate
terminal region arranged above the GaN/AlGaN
heterolayer region and electrically insulated
from the channel region in the associated
trench on the side wall. A common source
terminal region arranged above the fins is
connected to a first end of the channel region in
a vicinity of the upper sides. A common drain
terminal region arranged above the back side is
connected to a second end of the channel
region in a vicinity of the front side.
2405 route des Dolines, CS 10065
06902 Sophia Antipolis, France
contact@knowmade.fr
www.knowmade.com
KnowMade
54

Newsletter No. 16 III-N Technology

Transcription

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